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A note on water balance computation for use in climate-resilient agriculture and village level water conservation

planning

Hemant Belsare, Pooja Prasad, Milind Sohoni

CTARA, IIT Bombay

1.1 Introduction

In the past few decades, there has been rising agricultural distress all over the country,

especially in Maharashtra. One of the important reasons for this is climate change which is

manifested in terms of uncertainty in rainfall and increasing dry-spells and flooding events.

The stress is magnified in drought prone regions and areas with poor soil. While

Maharashtra has the largest number of dams in any state, the area under canal irrigation

continues to be small. Around 80% of the land in Maharashtra is under dryland or rainfed

agriculture with limited water resources and highly fluctuating crop yields which are largely

dependent on rainfall.

At the program level, there is a focus on the need to bring more area under agriculture,

increase productivity and farm incomes by providing assured sources of water for irrigation.

This has been primarily done through many watershed programs which rely on harvesting

rain water in a decentralized manner to augment groundwater and surface water. At the

same time, the limited water bearing capacity of the basalt rock which covers around 80% of

Maharashtra poses limits to recharge and extraction of groundwater resources (GEC, 1997).

Out of the total 353 talukas in Maharashtra, 28 talukas in Maharashtra are either semi-

critical or critical or over-exploited in terms of stage of groundwater development as per

GSDA Groundwater Assessment report of 2011 i.e. more than 70% of the available

groundwater is being extracted for various purposes, primarily agriculture. Out of these 28

talukas, the stage of development is more than 100% in 10 talukas (GSDA, 2011).

Thus, on the one hand there is a need to enhance agriculture through increased supply of

water and on the other, climate and geography pose serious limits on the supply itself

(Kulkarni Himanshu and P S Vijay Shankar ,2014). In such a situation, water balance becomes

an important tool which allows the planners to formulate the problem in terms of demand

and supply and provides scope for better planning. The water balance tool can be

implemented at various scales i.e. basin, sub-basin, watersheds, villages or even an

individual farm. Such a tool is helpful in comprehending issues regarding water security at

local and regional levels and is crucial to plan interventions as well as achieve community

understanding and consensus.

The following note explains different scientific water balance models in practice, their

components, relationships between components, spatial and temporal scales at which they

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are computed, the methods used to estimate/measure the components and their

application for different stakeholders. We will also describe a new water balance framework

through application of these scientific approaches to address key questions faced by dryland

agriculture. Such a framework can be used or applied at any spatial scale. One such model

based on this framework which is already used for village level water conservation planning

in Jalyukt Shivar Abhiyan program will be explained in detail. Another model based on the

same framework which can be used at farm level and is currently being designed for

government program Project on Climate Resilient Agriculture (PoCRA) will be explained in

brief.

1.2 Water budget and its science

The hydrological cycle forms

the basis of the water

budget. Its key components

include: precipitation,

surface runoff, stored

surface water, infiltration,

ground water storage and

discharge,

evapotranspiration from

vegetation, evaporation from

stored surface water and so

on. The total amount of

water in the hydrological

cycle is conserved due to

mass balance, which forms the central principle of the water budget.

A simple example – Following is a toy model for Germany which shows how the mass

balance in the hydrological cycle is achieved. This is a sub-cycle (or an aggregation) of the

main hydrological cycle which just explains how rainfall is converted into runoff, water

extracted by crops i.e. evapo-transpiration and groundwater flows. It shows how all the

water eventually goes back to atmosphere and is conserved. It assumes of course that, for

example, all no run-off emanating from outside Germany enters it. Indeed, in all water

balances, there is a chosen boundary, and flows across these boundaries need to be

estimated, or the boundary itself needs to be chosen judiciously. In the following section, all

these quantities will be explained in detail and models based on different sub-cycles of the

hydrological cycle and different boundaries will be described.

Figure 1 - Hydrological cycle (ref- USGS)

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Figure 2 - Simple toy model - Germany

1.3 Different water balance models in practice

The hydrological cycle is made up different sub-cycles like the one seen above. Different

sub-cycles have different stocks and flows. Various stocks and flows and the corresponding

sub-cycles are of interest to different stakeholders and agencies. For example, the

conversion of run-off to surface water storage is the primary domain of an irrigation

engineer while the changes in soil water stock are of concern to the farmer.

Depending upon the objective of the exercise, these balances can be done on a daily,

monthly, seasonal or annual basis. Moreover, they may be conducted across a farm

boundary, a village boundary or a watershed.

While in principle, such computations can be done at various scales and boundaries,

however, the key issue which concerns the agency using a particular model is that of

measuring or estimating the stocks and flows. Some quantities can be easily measured, like

rainfall while, some require complicated procedures for measurement like

evapotranspiration, while some can be only estimated, like groundwater stock. This poses

constraints on the boundaries and scales to be used as well as on the accuracy of the

models.

Three different such scientific water balance models are discussed below.

A. Regional surface runoff model

The system boundary for this model is the land surface of the chosen area. It can be a small

land parcel like a farm, a village or a watershed or the whole river basin depending on the

scale of interest. The key stock is the surface water stored or impounded within the system

boundary.

The most important incoming flow is the rainfall occurring within the boundary. The key

phenomenon in this model is the generation of surface runoff as rain hits the land surface.

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The two main products of this phenomenon are surface runoff and infiltration of the

remaining water into the ground.

The outgoing flows are the water which infiltrates below the land surface into the soil,

surface water which flows out of the boundary through streams, rivers, channels as runoff

and the part of the stored/impounded water which leaves to atmosphere as evaporation.

Surface water entering the boundary from outside through rivers, streams etc. is also an

important incoming flow but the boundary can be so chosen (say, watershed) which makes

this quantity redundant. For other boundaries (e.g. village), this quantity needs to be

measured / estimated.

The temporal scale can be a single rainfall event which lasts for few minutes or hours or can

be a single day, the whole monsoon season or the whole year.

Following is the schematic explaining the above model –

Figure 3 - Surface runoff model

Following are the equations which explain the above schematic –

--- Eqn 1

-- Eqn 2

Surface runoff is generated during the monsoon season. Part of this runoff that is

impounded is lost to atmosphere through evaporation, some infiltrates into the ground and

the rest is available as surface water. This when aggregated over the remainder of the year,

gives us –

-- Eqn 3

Eqn 3 represents the demand side in this model. The impounded surface water stock is

either directly utilized or transferred to different locations for irrigation, domestic or

industrial uses or is used locally as groundwater recharge available in wells.

The factors on which different components of this model depend and their methods of

measurement or estimations are explained as follows –

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a. Rainfall – this is measured using rain gauges at specific locations and frequency (hourly,

daily, monthly or seasonal). In case of low density of rain gauges, the rainfall is generally

extrapolated to nearby locations.

b. Surface run-off – this depends on factors such as the slope of the land, soil type, soil

thickness, land use pattern and the daily or hourly distribution of rainfall.

SCS (Soil Conservation Service) curve number (CN) method developed by USDA (United

States Department of Agriculture) is a popular method which is used to estimate surface

runoff generated by rainfall. It is based on the assumption that before runoff occurs, rainfall

must exceed the infiltration capacity of the soil i.e. runoff begins after some rainfall has

accumulated. The basic mathematical relationship is that the ratio of actual retention in soil

to potential retention in soil is equal to the ratio of rainfall to rainfall minus initial

abstraction (NIH, 2001). The relationship is reduced to only one parameter i.e. soil retention

parameter, which is associated with the Curve Number which lies in the range 0 to 100. The

assignment of CN values to soil cover and land use complexes was achieved by combination

of empirical data fitting and interpolation. Lower the CN, lower the runoff generated in that

particular soil cover and land use complex.

SCS method also introduces concept of Antecedent Moisture Condition (AMC) which is

based on the relationship between soil retention capacity and the current soil moisture.

Thus it considers three conditions, dry condition, normal condition and wet condition

depending on the rainfall in preceding five days. The CN changes according to these

conditions thus changing the runoff value. Runoff in dry condition is less than the runoff in

wet condition (Neitsh et. al. 2011).

When computing runoff over a region, the region is generally divided into HRUs (Hydrologic

Response Units) based on soil types, depths, land use and slopes. CN value is assigned to

each HRU and runoff is computed daily. Runoff is then aggregated spatially (across HRUs)

and temporally (across the season) to get seasonal runoff for the entire region (Neitsh et. al.

2011).

Strange’s table method – Another simple method developed by a British scientist, Strange

in 1870s is used generally in state driven programs. It is known as Strange’s table method.

Based on empirical data and field surveys Strange developed a table for estimating runoff.

Thus, it provides a lookup for the surface run-off as a fraction of total rainfall based only on

two factors – a) whether the average slope in the area is high, moderate or low and b) the

total rainfall in mm. This method is easy to use but does not consider factors such as daily

rainfall pattern, soil types, land use etc (Subramanya, 2008).

c. Infiltration – this is derived simply from the difference between rainfall and runoff for a

particular time step (i.e. hourly, daily, monthly or seasonal).

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d. Runoff impounded – this is the key component for the planners. The objective is to

impound the runoff and make it available for use. The amount of runoff impounded

depends mainly on the type of water impounding structure and its storage capacity. There

are different types of water harvesting structures, some are meant to only store the water

while others are meant to store water and help it recharge the nearby wells. Various types

of structures are cement bunds, earthen bunds, percolation tanks, farm level bunding,

contour trenches, terracing etc.

e. Evaporation losses – The runoff which is impounded by the water harvesting /

impounding structures is subject to loss through evaporation. Evaporation depends on the

temperature, humidity, wind speed and of course on the surface area of the impoundment.

Generally norms for the evaporation rates in different climatic zones are used to estimate

evaporation losses. The remaining water (impounded runoff – evaporation losses) is

considered as available for use. As per GEC norms, 50% of the water impounded is available

through groundwater recharge (GEC, 1997).

Application

This water balance model is extensively used by the agriculture department in Maharashtra,

for example in the centrally sponsored watershed program Integrated Watershed

Management Program (IWMP) and also the state sponsored Jalyukt Shivar Abhiyan (JSA)

program for the years 2015-16. Runoff is computed using the Strange’s table method.

In IWMP this model is used at the watershed level (around 5000 to 10000 hectares) while in

JSA it is used at village level (around 1000 to 2000 hectares). Taluka level rainfall is used and

is applied to all the villages in the taluka. Only annual rainfall is used.

The impounded runoff is measured by noting dimensions and storage capacity of the

interventions, number of times the intervention is filled during the monsoon season and

estimating evaporation losses by using the evaporation coefficients (Minor Irrigation

Manual of 1982).

A sample runoff computation for a village Marhal Kh in Sinnar taluka of Nashik district is

shown below. The rainfall is 492 mm and this rainfall is looked up in the Strange’s table and

runoff coefficients (or per ha runoff generated) for different slope categories are filled in the

table below to compute the total runoff.

Table 1 - Sample surface runoff budget (village Nanndur Shingote, Sinnar, Nashik)

Slope category Area (ha) per hectare runoff as per Strange’s table

runoff (TCM)

0-5% 656 0.333 218.45

5-20% 1452 0.502 728.9

greater than 20% 250 0.67 167.5

Total runoff 1114.85

Total runoff in mm 47.3 mm

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B. Soil water balance model –

The system boundary for this model is the soil layer just below the surface. This model is

basically a 1-d model explaining vertical movement of water in soil. The model can be used

over a single individual farm or group of farm parcels with similar soil characteristics and

crop characteristics. The temporal scale can be daily, weekly or for the whole crop or

vegetation life cycle or the monsoon season. The key stock is the water held in the soil layer.

This depends on the soil thickness and soil texture. Thick black-cotton soils may hold as

much as 200mm of water, while poor and thin soils may hold very little, and crops in such

soils may need frequent watering (WALMI, 1988).

The incoming flow is the infiltration, or the water entering the soil layer. This can be

infiltration from rainfall event or application of irrigation by farmer. Any vegetation planted

within the boundary extracts water from the soil layer through its root system for its

growth. Only around 2-3% of the water extracted by the roots stays within the plant system

while the rest evaporates to the atmosphere through its leaf surface. This process is called

transpiration. At the same time, the water held in the soil is also evaporated directly to the

atmosphere. These two processes are together called evapo-transpiration or ET. It is one of

the key outgoing flows (Allen et. al. SWAT Theory).

The other key flow out is the water which moves down the soil by gravity and enters the

murum or the shallow aquifer as groundwater recharge (GW recharge). The water left

within the soil layer is the soil moisture stock.

Figure 4 - Soil water balance model

Following are the equations which explain the above schematic –

-- Eqn 4

ET in the above equation represents the demand side and is of prime importance for plant

or crop growth. If the full crop cycle is considered as the time scale, then the supply side can

be infiltration from rainfall or irrigation provided by farmer or combination of both. The

factors on which the key components depend and their methods of measurement /

estimation are explained below –

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a. Evapo-transpiration –

It can be called as water requirement of a plant / crop and as explained above, it is

combination of evaporation of water from the soil surface and transpiration of water from

the plant leaves. Evaporation and transpiration occur simultaneously and there is no easy

way of distinguishing between the two processes.

ET is measured as rate of water being lost to atmosphere and is expressed as mm per unit

time. The time unit can be an hour (mm/hour), day (mm/day) or the entire growing period

of the crop (mm/season) or year (mm/year).

It depends on the weather conditions i.e. radiation, temperature, humidity, wind speed etc.,

on the crop characteristics i.e. the crop development stage, leaf area, root system, the crop

variety, the method of irrigation etc. as well as on the availability of water in the soil. Typical

values of ET for crops range from 3 to 9 mm per day depending on the weather conditions

and the crop growth stage (Allen et. al. SWAT Theory). Typical values of crop ET considering

the whole crop duration range from 250 mm for short duration crops like moong, udid to

about 2000 mm for yearly crops like sugarcane in Indian conditions (WALMI, 1988).

There are two terms related to evapo-transpiration – i) PET is the potential evapo-

transpiration which depends only on the climatic factors. PET is multiplied with Kc, the crop

coefficient to get the crop PET. Kc depends on the crop characteristics. ii) AET is the actual

crop evapo-transpiration i.e. the amount of water which crop is actually able to extract from

the soil.

Thus, crop PET is nothing but the requirement of water on a particular day in the crop

growth stage depending on the climatic factors. Now, if the crop gets the required water

from the soil, the AET equals PET and the crop water requirement is satisfied. If AET is less

than PET, then the crop is in stress and after some point starts affecting the crop yield. The

soil moisture below which even plants cannot access the water is known as the wilting point

(WP) of the soil while the point till which free movement of water due to gravity occurs is

termed as field capacity (FC) of the soil. The moisture available to plants is between FC and

WP and it depends primarily on the soil texture (Allen et. al. SWAT Theory).

Pan evaporation is an experimental method used to calculate PET for a reference grass crop

which covers the ground surface and is never short of water. PET can also be estimated by

other theoretical methods based on energy balance like Penman Monteith method

(Monteith, 1965; Allen et.al. 1989), modified Penman Monteith method, Priestly-Taylor

method (Priestly and Taylor, 1972), Hargreaves method (Hargreaves et.al. 1985), Blaney

Criddle method and so on. These methods require solar radiation, air temperature, wind

speed etc. for estimation.

Thus, this model can help in identifying how the crop behaves under stress. CROPWAT is

one the models in practice, mostly by academicians and agronomists (Surendran U et. al.,

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2015). This model can also be helpful in understanding impacts of dry spells in monsoon

season on the crop water deficit, and hence on the yields.

b. Groundwater recharge –

The water infiltrated into the ground enters soil and starts filling up the pore spaces in the

soil. Once all the pore spaces are filled i.e. the soil is saturated, the water then starts moving

down freely under gravity, leaves the soil layer, passes through the shallow aquifer (murum

and weathered rock) and finally joins the water table i.e. groundwater. Groundwater

recharge is also a rate expressed in mm per unit time. The amount of water leaving the soil

layer per unit time depends on the soil moisture (i.e. whether soil is saturated or not), soil

porosity, the hydraulic conductivity of the saturated soil and soil thickness (Eilers et. al.,

2007). This model is used extensively to estimate groundwater recharge from rainfall (Raes,

2006; Panigrahi et. al. 2002; Lhomme, 1991).

A simple example of the soil water balance model is shown below –

The soil considered is a clayey loam soil of 40 cm and available water content of 20%

(WALMI, 1988). The porosity of the soil is 40% i.e. maximum 160mm of water can be held by

the soil. Water exceeding this limit would be converted to runoff. Thus, the water stock

available for crop is 20% of 40 cm i.e. 80 mm. From this stock, crop will be able to extract

water daily. Crop water requirement (cwr) per day is assumed to be 6mm. Groundwater

recharge occurs when water exceeds Field Capacity (i.e. 80mm). The model is run daily and

can be run for the entire season. A snapshot of the model is shown below.

Table 2 - Sample daily soil water balance model (hypothetical)

Component Label d1 d2 d3 d4 d5 d6 …..

Initial Soil moisture stock (mm) a 0 9 8 0 0 39 …..

Rainfall (mm) b 20 0 0 0 75 80 …..

Surface runoff (mm) c 5 0 0 0 15 15 …..

Infiltration (mm) d= b – c 15 0 0 0 45 65 …..

Soil moisture stock (mm) e= max (a + d, 160)

15 9 3 0 45 104 …..

Crop water uptake (mm) f = max(cwr, e) 6 6 3 0 6 6 …..

GW recharge g = min(0,e-80) 0 0 0 0 0 18 …..

Soil moisture stock at the end of the day (mm)

h = e-f-g 9 3 0 0 39 80 …..

C. Groundwater balance model –

The system boundary for this model is the shallow or the unconfined aquifer which starts

just below the soil layer. The spatial scale can be administrative boundary like village or

geographical boundary like micro-watershed, basin etc. The time scale is usually seasonal or

annual since groundwater movements are usually a few meters per day or lower.

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The key stock in this model is the groundwater stock in the shallow aquifer which is

accessed through open dug wells or shallow borewells. Aquifer properties like hydraulic

conductivities, specific yield, transmissivity etc. are understood only over broad regions and

thus, this is essentially a regional model.

The incoming flow is the water which percolates below the soil layer during the monsoon

season, after crops have taken their share. This happens across the spatial extent within the

boundary (except at places which are very steep or places with rock outcrops). This is called

natural groundwater recharge from rainfall (GEC, 1997). Apart from this, the standing

surface water impounded by water harvesting structures and the running water through

canal irrigation system also infiltrates into the ground and passes the soil layer to enter the

aquifer system (GEC, 1997). This is termed as artificial recharge and is available locally.

Another incoming flow is the lateral groundwater flow across the system boundary, e.g.,

when the surrounding hills feed groundwater into our chosen area. Again, if the natural

spatial extent is chosen say watershed or basin, then these cross flows can be assumed to

be negligible.

The important outgoing flow is the water extracted from the shallow aquifer i.e. the open

dug wells and the shallow borewells for drinking, agricultural or industrial purposes.

Another important outgoing flow is the groundwater flowing out of the system boundary.

This is termed as natural discharge and is an important component, especially in hilly terrain

where these flows are significant (Camp et. al., 2015). Water entering into the deep aquifers

is also an outgoing flow which is generally assumed to be negligible and is very hard to

estimate or measure especially in hard rock basalt where the only conduits of water are

cracks and fissures.

The groundwater recharge happens during the monsoon season and the discharge i.e. the

outgoing flows occur for the entire year. The water levels in the open dug wells rise during

the monsoon season and start declining as per the extraction and natural discharge for the

remaining part of the year. Thus, this shallow aquifer keeps on getting recharged and

discharged every year. Hence these are also called as dynamic groundwater resources (GEC,

1997).

Figure 5 - Groundwater balance model

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Following equation explains the above schematic –

--- Eqn 5

The components are estimated as follows –

a. Natural GW recharge – One way to estimate this quantity is by using the point-based 1-d

soil water balance model described above. Another well known regional method is the

water-level fluctuation method (Dewandel et. al. 2010) in which the water levels in the open

dug wells or shallow borewells before the monsoon season and after the monsoon season

are recorded. The difference (i.e. rise) in the water levels is due to the water infiltrating past

the soil layer. The average rise in well water levels is multiplied with the total area of the

system boundary and with the specific yield of the aquifer to get the total volume of

groundwater recharged. Typically the specific yield for the basalt aquifers in Maharashtra

ranges from 0.5%-15%. Lower the value of specific yield, lower is the capacity of the aquifer

to hold and transmit water.

GW flows and baseflows – The water which percolates below the soil layer and joins the

water table is in constant motion. This motion is guided by the conductivity and

transmissivity of the aquifer material and the topography of the terrain i.e. the gradients

created due to elevation difference. Water always moves from high gradient to low gradient

may it be surface water or the groundwater (Harbaugh et. al. 1988). During this motion,

groundwater may again enter back on the surface through springs. These are called

baseflows.

Within a watershed, there are regions where the GW recharge is significant. Generally these

are the upland regions with slopes and soils favorable to more recharge. These are called

recharge zones. Similarly the low lands or the regions adjoining the valleys with low slopes

and good soils are the regions where recharge is low but the availability of groundwater is

high due to the groundwater flows from the recharge zones. These are called discharge

zones.

There are methods to estimate the groundwater flows from recharge to discharge zones.

These methods are based on Darcy’s law which is used to compute groundwater flow

through any material. One of the most popular 3-d model which simulates the terrain,

geology and the flows is MODFLOW. (Harbaugh et. al. 1988) This model requires the

elevations, aquifer depths at each cell in the boundary, GW recharge as the input at each

cell, the starting head in each cell, the aquifer properties like hydraulic conductivity, specific

yield etc. and thus is very complicated in terms of data requirements and sensitivity to

errors in input data.

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The groundwater flows are negligible in flat terrains where the groundwater table is far

below the surface (Perrin et. al. 2012).

GW extraction – This is the most important component of the groundwater balance model.

It represents the demand side. Measurement or estimation of GW extraction is thus an

important activity and needs to be fairly accurate in order to determine the sustainability of

the groundwater resources. One way to estimate it is to study the nature of extraction

pattern from a single well and apply it to the total number of wells within the boundary.

Nature of extraction pattern varies with quantity of water extracted per day or per season

for different uses such as agriculture, drinking water and industry.

Another way is to see the demand side picture and estimate the extraction. In agriculture

for example, based on the cropping pattern within the boundary and crop water

requirement or the ideal number of waterings for different crops, the total extraction can be

estimated.

Application

GSDA GW Assessment – This model is based on the Groundwater Resources Estimation

Committee (GEC) methodology. The boundary is the watershed. The whole Maharashtra

state is divided into 1531 watersheds. The time scale is the whole year. Recharge is

estimated using the water-level fluctuation method. Around 5-6 wells are monitored for this

purpose at 4 times during the year. Along with this, the recharge through canals and water

harvesting structures during as well as after monsoon is added to total recharge. Natural

discharge is assumed to be 10-15% of the total recharge. GW extraction is estimated using

unit draft per well which is then multiplied with the total number of wells as per MI well

census. The result of the exercise is the stage of development of the watershed i.e.

proportion of GW used against that was available through recharge (GEC, 1997). Note that

the transition from soil moisture to groundwater recharge is only indirectly inferred.

Groundwater balance for a sample watershed is show below –

a) Watershed details

Table 3 - Sample example of GW balance (watershed details)

District Aurangabad

Name of watershed GV 53

Area 35417 ha

Rainfall 523 mm

Rock type and specific yield Weathered basalt , 0.02

Rise in groundwater level from pre to post monsoon ~4.76 m

No. of wells (irrigation dug wells + irrigation borewells) ~ 4000

Unit draft of dug well 1.21 ham

Unit draft of bore well 0.43 ham

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b) GW balance- (all numbers below are are in ham i.e. hectare meter)

Table 4 - Sample table of GW balance (water balance components) – (GSDA, 2011)

Watershed

Recharge from rainfall during monsoon

Recharge from other sources during monsoon

Recharge from other sources during non monsoon

Total annual GW recharge

Provision for natural discharges

Net annual GW avail-ability

Total GW draft

Stage of devpt (%)

GV-53 1826.57 113.99 2981.56 4922.22 246.11 4676.11 3813.4 81.5

2. Water security issues in agriculture

In the above section, three different water budget frameworks and the corresponding

specific models in practice were presented. These models dealt with different stocks and

flows and catered to different demands like i) the need to impound maximum surface run-

off in order to harvest maximum rainwater for human consumption, ii) the need to monitor

/ determine soil moisture in order to address crop water stress and provide timely irrigation

and iii) the need to monitor and assess groundwater availability and its use, and identify

critical and over-exploited regions and to inform regulators to ensure ecological

sustainability.

This section will try to identify the issues and challenges faced by the farmers with regards

to water security. This will help in the design of a suitable water budget framework.

The main problems faced by the farmers are:

(i) low, erratic rainfall, increasing rainfall intensity (i.e. decreasing number of rainy days and

increasing number of dry spells)

(ii) subsequent impact of dry spells on kharif crop productivity, especially for farmers with

poorer soils, reduction in crop productivity and the inability to provide protective irrigation.

(iii) increased groundwater stress during rabi season, and

(iv) increasing farmer demands and aspirations to go for cash crops and new mechanisms

for getting water.

We will see these issues one by one.

(i) Rainfall –

In Maharashtra, most of the rainfall is received from the south-west monsoon. Monsoon

starts in the month of June and ends in the last week of September or sometimes in the first

or second week of October. Some parts of the state i.e. the eastern region of Marathwada

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and the entire Vidarbha also receive some rainfall from north-east monsoon which occurs in

the months of October to December.

Several attempts have been made to understand the behavior of the south-west monsoon

rainfall in different agro-climatic regions on the basis of historical rainfall records. As per

these studies (Singh, 1986) i) there is large variation in dates of commencement of south-

west monsoon from year to year and in different parts of the country, ii) monsoon rainfall

often comes with long dry spells and breaks which sometimes extend up to one month or

even more, iii) there is large variation in the date of withdrawal of monsoon from year to

year and iv) there is variation in quantum of rainfall received from year to year in different

parts of the country.

See for example, Parbhani taluka’s rainfall from 1999 to 2017. It can be seen how the

rainfall has deviated from the normal rainfall over the years. The highest rainfall between

these years is 1168 mm in 2005 whereas the lowest has been 364 mm in 2015. Although the

normal rainfall for Parbhani taluka is around 800 mm, the rainfall fluctuates widely from

year to year and is prone to uncertainty with frequent bad rainfall years.

Figure 6 - Parbhani taluka rainfall (source - www.maharain.gov.in)

Apart from yearly variation in rainfall, the intra-year variation is also substantial. This

variation can be in terms of delayed onset of monsoon or long breaks in between or early

withdrawal of monsoon. Several studies have also shown that the number of rainy days

have reduced, while the rainfall intensity and duration of dry spells has increased over the

last 50-60 years (Singh et. al., 2010; Mishra et. al., 2014).

For example, see below the rainfall distribution for Sangamner (Ahmednagar district) for

two years 2016 and 2017. The SCS CN method described in section 1.2 A is used here.

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Figure 7 - Sangamner (Ahmednagar) 2016 daily rainfall

Figure 8 - Sangamner (Ahmednagar) 2017 daily rainfall

The total rainfall is similar during these two years, but the pattern varies. 2017 rainfall starts

on time, i.e. in the first week of June, is more distributed in nature with more number of

rainy days and less number of long dry spells, the 2016 rainfall begins late (i.e. 3rd week of

June), has less number of rainy days and a long dry spell lasting for more than a month

during August and September months which are crucial for crop growth.

(ii) Impact on agriculture

Dry spells –

In Maharashtra, kharif season (i.e. June to September) is an important season for cropping.

Most of the farmers sow their entire cultivable lands during kharif season in the hope of a

good rainfall. In case of dryland agriculture, soil moisture is the main source of water and

hence the occurrence of dry spells has a large impact on the crop productivity and hence on

the farm incomes. Thus, the farmers who solely depend on the kharif crop suffer badly due

16

to such dry spells. See below for example the entire crop cycle for soybean crop for the

above monsoon rainfalls for Sangamner of 2016 and 2017. A variation of the soil water

balance model discussed in section 1.2 B is used here (CTARA, 2017).

Figure 9 - Soybean PET vs. AET - Sangamner (2016) for clayey loam soil

Figure 10 - Soybean PET vs. AET - Sangamner (2017) for clayey loam soil

The x-axis in the above graphs is the days, starting from 1 i.e. June 1 to 154 i.e. October end.

The orange bars show daily rainfall. Daily rainfall (right hand side y-axis) varies from 0 mm to

about 60 mm in this case. The green line shows the daily crop water requirement for

soybean crop from sowing to harvest (left hand side y-axis). It ranges from 1.5 mm to about

5 mm per day depending on various crop growth stages. The blue line depicts the water

available for the crop through soil. If the rainfall amount and its distribution is adequate, the

blue line will always coincide with the green line and there will be no deficit.

In above cases we see the gaps between green and blue lines during dry spells. This is the

crop water deficit. It can be seen that the during year 2016 there was a long dry spell and

17

the crop water deficit was about 100 mm i.e. almost 25% of the crop requirement. This

happened at the crucial stage of the crop growth when more water was required. This has a

large impact on the crop productivity especially to crops like soybean which are relatively

less tolerant to soil moisture stress.

In the year 2017, the total rainfall was similar to last year’s, but there were two short dry

spells instead of a long dry spell. In this case the crop water deficit was around 50 mm i.e.

half that of previous year. This shows that the rainfall distribution is a very important

determinant when it comes to kharif crop productivity (Viswanathan, 2017).

Spatial differences within village

As seen in the above section, uneven distribution of rainfall within season and the presence

of dry spells lead to crop productivity loss. But this loss is not equally experienced within the

village. Some farmers can cope with the dry spells and suffer mildly while others suffer

badly. This depends on the natural / geographical factors like soil types, location of the farm

(slope, nearness to stream etc.) and on socio-economic and infra-structural factors like

having a well, drip/sprinkler sets, ability to transfer water from long and short distances,

ability to buy water during water stress periods etc.

Here we focus more on the geographical / natural factors which decide the crop

productivity and farm incomes. As we know, some soils like clayey, clay loams etc. with

good soil thickness are good for moisture retention while soils like sandy, gravelly etc. with

less soil thickness cannot retain water for longer duration. Thus, during a dry spell, a clay

loam can hold water for few more days than a gravelly sandy soil (Barron, et. al., 2003). This

helps the crop to survive more and reduce loss in productivity. This can be seen in the

example below. We consider the same Sangamner rainfall for the year 2016 when there was

a long dry spell and see its effects on a clay loam soil with thickness 1 m, and a gravelly

sandy loam soil with thickness of 40 cm.

Figure 11 - Soybean PET vs. AET - Sangamner (2016) for clayey loam soil

18

Figure 12 - Soybean PET vs. AET - Sangamner (2016) for gravelly sandy loam soil

Above two graphs clearly show that for the same crop, i.e. soybean and for the same

rainfall, the two soils clayey loam and gravelly sandy loam behave differently and lead to

different results as far as crop water deficit and crop productivity are considered. The

soybean in gravelly sandy loam suffers 200 mm of water stress i.e. almost half the crop

water requirement. Most of the stress occurs during the long dry spell of about 35-40 days

during August and September. The crop gets no water for around 25 days which can lead to

serious reduction in yield and even complete crop failure.

Whereas the soybean crop in clayey loam suffers around 100 mm of water stress, but even

then there is not a single day when crop gets no water from the soil. This results in some

productivity loss but less as compared to soybean in gravelly sandy soil.

Thus, it is important to understand the impact of dry spells on the crop productivity. Also it

is important to understand the differences in soil type, thickness and overall land capability

within the village or watershed. It is also clear that a soil map can be effective in identifying

vulnerable farmers which will help further to plan interventions for them.

(iii) Rabi season water use –

Rabi cropping depends on availability of residual soil moisture from the monsoon season

and also on the availability of groundwater. Generally in the dryland regions, groundwater is

not available in abundance everywhere in the village. In Maharashtra, this is mainly due to

geological and geographical constraints. Thus, only few farmers can access the groundwater

and take two and even fewer can take three crops.

The main objective of watershed programs is to stop the runoff and impound it in water

conservation structures during monsoon and make it available for use as groundwater

through wells during rabi season. The water conservation structures help in local

groundwater recharge and increase the availability of water in the nearby wells.

19

Hence, nearness to these water conservation structures like cement bunds, percolation

tanks or nearness to streams which flow for some months post-monsoon can increase water

availability enough to take rabi crop (Belsare, 2015; Belsare, 2016).

Apart from the locally increased groundwater availability due to water conservation

structures, the availability of groundwater at a particular point is also decided by the

topographical and geological factors. A farm in the recharge zone of the watershed with

poorer soils will help in more natural groundwater recharge during the monsoon season but

will not be able to hold the groundwater due high conductivity and gradients. A farm in the

discharge zone with good water holding soils will restrict groundwater recharge during

monsoon season but will receive groundwater flows during the post-monsoon season. This

mainly happens in the villages with hilly terrain.

The area under rabi agriculture in a village is generally in the range of 20-40%, sometimes

even less than 20% depending on the terrain, geology, rainfall and soils. But with more and

more farmers aspiring to take rabi crop, and with increased density of wells and increased

extraction, if more land is brought under rabi crop with the same rainfall and groundwater

availability, then crop yields will suffer due to shortage of water. Thus, an estimate of the

water available at rabi is an important input to farming decisions.

(iv) Farmer aspirations and the question of sustainability

Another important objective of any watershed program is to increase the area under rabi

and summer crops so that more and more farmers are able to grow more than one crop and

thus increase their farm income. For the farmers already growing rabi crops, the aspiration

to grow more remunerative and cash crops is equally important. Horticulture and

vegetables provide avenues towards such increase in incomes. But looking at the current

scenario, the more remunerative the crop is, more is the water required for the crop (WRG,

2015).

Figure 13 - Water in litres per rupee of output and crop water requirement (mm) for various crops

20

It is clear from the above graph that crops like horticulture, vegetables, sugarcane etc.

which require more water are actually more remunerative in terms of cash value created.

Thus, as more and more farmers aspire to grow cash crops, more crucial will be stress on

water. Also, along with the quantity of water required per unit of extra money earned, the

timing of water requirement is also important.

For example, fruits like pomegranates, grapes, oranges are multi-year crops and require

assured water at crucial times during summer. In such a situation farmers are ready to

invest in deep borewells or plastic-lined farm ponds for storing water or transfer of water

from long distances. With limited water resources, few farmers using more water may

directly or indirectly come into competition with small and marginal farmers who depend

only on traditional crops like jowar, bajra, wheat, tur etc. for their livelihoods.

This brings an important responsibility on the watershed programs, so as to prevent such

adverse effects while planning for increased supply for the aspiring farmers. In such

situations too, the seasonal water balance will be an important tool for analysis.

Example

Figure 14 - Jam watershed - farm ponds

An extreme example is Jam watershed, which lies in the eastern part of the Sinnar block of

Nashik district and runs from south to north. The size of the watershed is around 300 sq.

km. The elevation difference between the upstream and downstream is around 200m,

highest elevation around 720 m asl. and lowest around 520 m asl. The average rainfall in the

watershed reduces from 450-500mm at Nandur Shingote, in the upper catchment down to

about 300mm in the downstream areas.

The red lines are the canals which bring water from the Bhojapur dam situated in the

neighbouring watershed on the south. The water is supposed to provide protective

irrigation to the downstream villages in the Jam watershed. The purple dots in the above

21

picture are all farm ponds out of which around 90% are plastic-lined farm ponds. The main

purpose of these farm ponds is storage of water throughout the year for watering

horticulture crops like pomegranate. These are filled by water from the wells, during

monsoons, and irrgation water during the rotations. This of course, adversely affects

downstream farmers.

In summary, following are some of the key issues on the ground, which need to be

addressed in the water budget framework:

1) assessment of AET and the protective irrigation requirements during kharif dry spells

2) identification of vulnerable farmers and better information on locations and quantity of

water harvesting required, so as to inform design of interventions.

3) better information of the water stocks, both impounded run-off and groundwater, at the

start of rabi season and the suitability of the cropping pattern and area to be sown

4) water budgetary limitations to farmer aspirations for horticultural crops and issuance of

warnings about unsustainable cropping patterns

5) better analysis of some of the success stories in the sector, such as Kadwanchi or Hiware

Bazar.

3. Water budget architecture–

As we have seen in the previous sections, the demands at the farm level are about assuring

kharif crop, stabilizing and increasing crop productivity, increasing area under agriculture

(rabi and summer crops), shifting to more remunerative crops and so on. On the other side,

there are climatic, geographical and other natural factors which control the supply side, like

rainfall, its daily distribution, soils, geology, topography etc. which can be clubbed together

as the biophysical supply side.

The engineering supply side comprises of harvesting structures which impound water, and

supplement the bio-physical supply side. But the questions such as how much to impound,

where to impound, for whom to impound, how the farmers would use the impounded

water, when would they use, which crops should they grow with the increased water etc.

are also significant. There are limits to increasing supply side and there are no limits to the

demand side.

Thus, the ideal architecture would integrate both the supply side and the demand side, the

engineering infrastructure as well as bio-physical cycles of water, the temporal scale of the

seasons, as well as the spatial scales of the farm with the regional scales, which may be

administrative or hydro-geological.

22

Following schematic explains the demand-supply picture which must form the basis of the

water budget framework –

Figure 15 - Farm level and regional level water balance and planning

The budget is a combination, primarily of the farm-level soil water balance, and the run-off

utilization at the zonal/regional level. On the right are farms and land parcels clubbed by

land-use and bio-physical attributes such as soil-types, daily rainfall data. This data is to be

used to run the farm-level water balance wherein run-off, recharge as well as AET are

estimated at the farm level. This leads to a computation of the farm-level stress and the

protective irrigation demand. On the left are the key stocks of surface water and

groundwater, which are essentially regional, and the engineering structures which harvest

run-off and make these stocks available to the farmer.

Going from right to left, is to follow the flow of water, and of numerical and geographical

aggregation into the regional stocks, while going from left to right, is the satisfaction of

demand by irrigation, and the socio-technical process of providing access to water for

individual farmers.

Thus, an ideal framework must run multiple copies of the farm-level water balance at the

daily and local scale, and the surface-water and groundwater balances on the regional scale,

and provide computational linkages between the same. We describe here an attempt in this

direction. Later, we also describe somewhat light-weight adaptations of the same which

have been adopted by GoM in their Jalyukt Shivar program for a village level water balance.

23

The same demand-supply framework can be depicted as below in an Up-Down instead of a

left-right manner. It serves to highlight the seasonality of the water balance computation

process. The two key points here are i) protective irrigation requirement and booking of

surface water stock for avoiding soil moisture stress during kharif season and ii) important

decision just before rabi and summer seasons about how much and what to cultivate with

regards to water availability.

Figure 16 - Water budget framework - conceptual diagram

4. The model

Based on the above architecture, following is the water budget model which can be used for

the village / cluster /watershed level planning of interventions.

Figure 17 - Farm-centric regional water balance model

24

The main computations of this model are –

i) Kharif season analysis – This consists of three steps –

a) Estimation ofcrop water requirement and various flows at a given point on daily basis

during kharif growing season

This is the core engine of the framework. It conducts daily water balance for a point location

with given soil properties, crop and other land properties. This computation is based on the

soil water balance model described in section 1.2 B) above with the assumptions therein.

Daily rainfall data available at revenue circle level at maharain.gov.in is used. Soil and land

use data from MRSAC maps are used to get soil texture, soil depth and other properties

required for the model. Cropping data from Taluka Agriculture Office is used. Alternatively,

primary field surveys can be conducted at farm plot level to collect all the above

information. The outputs of the net planning exercise developed by WOTR and used in

IWMP may also be modified to include the data inputs required for this model.

The main outputs of this model are surface runoff, soil moisture stock, actual crop evapo-

transpiration (AET) and natural groundwater recharge on a daily time step.

b) Computation of farm-level stress and vulnerability

Once the crop water requirement (PET) and the crop AET are known, the difference

between the two is the stress, which is calculated at daily level for all points in the

agricultural area. This kharif deficit is aggregated for the whole monsoon season to compute

total excess water required at given field and is marked on the map. This map when overlaid

over revenue map to identify the vulnerable zones and farmers which should be prioritized

for any watershed intervention. Following is the example for the Gondala cluster (villages

Lingdari, Gondala, Jamdaya and Umardari) in Sengaon taluka of Hingoli district.

Figure 18 - Gondala cluster kharif season crop water stress

25

ii) Runoff analysis and kharif deficit mitigation target

Here the regional surface runoff is computed using the surface runoffs computed at all the

points and aggregated at suitable exit and entry points. Indeed, for any point chosen on the

stream, one may compute the total runoff generated in its upstream. Such points may be

chosen close to the regions of kharif stress displayed above to obtain run-off available for

harvesting at suitable sites.

For the Gondala cluster, Fig. xxx shows daily circle rainfall (on the left hand side) and the

runoff calculations for two points of interest on the drainage lines on the right hand side.

different streams especially at points closer to kharif stress areas.

Figure 19 - Gondala cluster - runoff analysis

iii) Rabi groundwater balance

This computation consists of estimation of the total available water (in the form of soil

moisture and groundwater) at the end of kharif season and then matching the stock with

the crop water requirement in the rabi and summer season.

This is done at regional level i.e. the entire boundary of the system (i.e. village or

watershed). The inputs to the estimation process are i) net groundwater recharge in kharif

season which is as computed above at point level, ii) soil moisture available at the end of

kharif season which also is as computed above and iii) the planned rabi evapo-transpiration

load in mm. This may be computed by deciding the crop-mix to be taken and computing the

net ET load.

The main output of this process is the Rabi Water use index which indicates the proportion

of available water used by rabi and summer crops.

Please refer to pocra note for more details (CTARA, 2017).

26

5. Adaptation to Jalyukt Shivar village plan –

Jalyukt Shivar Abhiyan (JSA) is a flagship program of Government of Maharashtra which was

launched in the year 2014. JSA is essentially a village-level program with the main aim of the

making all villages in Maharashtra drought-free and self-sufficient in terms of agriculture

and drinking water needs.

The main objective of the program is to create decentralized water storages at village level

through soil and water conservation activities like contour trenches, compartment bunding,

earthen bunds, cement bunds, percolation tanks, nala-deepening etc. as well as through

repairs and desilting of existing interventions.

Water budget forms an important planning tool in JSA. It is to be executed by the Krishi

Sahayak (the village level official in Agriculture department) who has to plan the

interventions based on the output of the water budgeting exercise and in coordination with

other departments and village representatives.

The program has been implemented in around 5000 villages every year since 2015. For the

year 2017-18, it was decided by the Secretary, Water Conservation Department (WCD) to

move away from the surface runoff budget used in earlier JSA villages i.e. 2015-16 and

2016-17 and to introduce a holistic and integrated water budget which focuses on all

aspects of water security at village level.

The requirements of the water balance model in JSA were as follows –

i) the model should be as simple as possible, easy to understand by a lay-person and should

be computable by the Krishi Sahayak at the village level

ii) the overall implementation and planning should remain unchanged as far as possible

iii) the model should make use of available datasets as far as possible and should be

implementable with in all the villages.

Based on the above requirements and constraints, it was decided to develop a simple water

balance which would be based on the water budget framework discussed above, but

aggregated to village level.

Based on these constraints the above framework is simplified as follows –

In this model, runoff is computed currently, at village level, and by using Strange’s table

method. Runoff is computed for the whole monsoon season using rainfall data for the entire

season. So both the temporal and spatial scales are at the aggregate level.

27

Figure 20 - Jalyukt Shivar water balance architecture

Aggregate cropping data is available at village level through pik perni ahawaal. This data is

used to compute the entire kharif ET and rabi + summer ET separately.

The rainfall minus the run-off (which is infiltration) is counted on the supply side and not

bifurcated into soil moisture and groundwater recharge. As farm level water balance is not

computed, it is not possible to compute soil moisture stress and availability at the farm

level. Soil moisture stress at farm level is important in identifying the vulnerable zones and

planning for the protective irrigation demand. But this is compensated in this budget by

assuming protective irrigation demand as 10% of the total kharif crop water requirement. If

the soil map is examined carefully, the interventions may be planned in the regions of poor

soils so as to meet this requirement.

This infiltrated water minus the kharif crop water requirement is the water available for the

rabi and summer season.

The runoff computed at village level is impounded by existing water harvesting

interventions. This amount (after subtracting evaporation losses) is available for kharif

protective irrigation as well as for the rabi cropping.

Rabi water use index is the ratio of total rabi and summer crop water requirement to total

water available at the beginning of rabi season. If the index is greater than 1 it means that

more water is used than is available.

The detailed computation steps are shown in Appendix I while an example for village Marhal

in Nashik district is shown in Appendix II.

28

The protective irrigation demand, water available at the end of kharif season and rabi water

use index are some of the key outputs of the JSA village water budget exercise. These

outputs need to be interpreted along with few other proxies like area under rabi cropping,

area under kharif cropping, type of crops, percentage of areas with poor soils, percentage of

runoff impounded by existing interventions as well as by newly proposed interventions etc.

in order to comprehend the situation in the village correctly. This will help in better planning

of interventions. Following is a sample table for interpreting the water budget –

Table 5- Few interpretations from JSA water budget

Indicators Value Meaning Remedy

Total water available at the end of kharif

negative High proportion of annual crops which depend on borewells or external water OR high proportion of long kharif rainfed crops like cotton and tur which very have low yields

Area under horticulture / annual crops need to be brought down, regulation on borewells OR more runoff to be impounded near to area under rainfed crops

Rabi water use index

< 0.5 Too less area under rabi cropping, and most of the rainwater flowing out of the village boundary

More runoff needs to be impounded, soil erosion needs to be checked. Runoff

impounded / Runoff generated

too less

Rabi water use index

< 0.5 Even after impounding substantial runoff, rabi cropping is low. This can happen in very low rainfall areas

Major focus should be on protecting kharif crops.

Runoff impounded / Runoff generated

>= 0.7

Rabi water use index

>= 1 No scope for further water conservation structures

Focus should be on regulating demand through increasing water use efficiency or cropping pattern changes

Runoff impounded / runoff generated

>=0.7

This water budget framework is amenable to changes in terms of data availability and more

scientific research. It can be taken closer to the farm-centric regional water budget as

discussed in section 4. This may require more data to be collected at farm level, use of maps

which are already available with MRSAC, more computations, more steps and more tables

to be filled at village level. But such a budget will help understand crop stress in kharif,

identify vulnerable zones and more exact locations of interventions. It will help JSA to

achieve har khet ko pani, the main objective of the PMKSY (Pradhan Mantri Krushi Sinchai

Yojana) program.

29

References

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semi-arid hard rock regions: application to a rural watershed in South India” – Wiley

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of Water Resources, Government of India

30

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available online at gsda.maharashtra.gov.in

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www.ScienceDirect.com.

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irrigation – Case studies” – Report by Revitalising Rainfed Agriculture Network (RRAN) and

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31

Appendix I

JSA water budget computation steps –

1. Total rainwater available –

The main inputs are seasonal rainfall and the total area of the village watershed (i.e. micro-

watershed which best coincides with the village boundary).

The output is the total rainwater available in the kharif season.

*** TCM is thousand cubic meters

2. Total surface runoff generated

This is computed by using seasonal Strange’s table method as described above in section 1.2

A). The inputs required here are the areas within the village with respect to slope

categories.

Slope Area (ha) Per ha. runoff

generated (TCM)

Runoff generated

(TCM)

0-5 %

5-20%

more than 20%

Total surface runoff generated

3. Surface runoff impounded by existing soil and water conservation structures

Intervention units

Number /

ha

Storage

capacity

(TCM)

Evaporation

coefficient

(%)

Usable

water

(TCM)

Number of

fillings

Total water

available

(TCM)

CCT

Compartment

bunding

Farm ponds

(inlet-outlet)

32

Earthen

bunds

Cement

bunds

Nala

deepening

and widening

Percolation

tanks

Repair works

Total

The storage capacity for each structure needs to be measured on the ground, considering

the siltation happened and the age of the structure. For area treatment structures like CCT

and compartment bunding, norms of soil excavation per hectare can be taken as the storage

capacity created.

Evaporation coefficients are taken from the Minor Irrigation Manual of 1982 for various

structures.

Number of fillings is to be filled as per the observations on the field and the rainfall pattern

of that year.

4. Drinking water requirement –

Population DW requirement (lpcd) Total annual DW need

Humans

Cattle

Sheep / goats

Small livestock

(poultry)

Total

5. Total kharif crop water requirement

33

Village level pik-perni ahawaal or crop-sowing report which is available at the TAO office is

used for computing the total kharif crop water requirement. The crop water requirement

for each crop is taken from the WALMI booklet. WALMI institute of Aurangabad has

estimated seasonal crop water requirements of different crops for different agro-climatic

zones by doing pan-evaporation measurements at different locations. These crop water

requirement values along with area under each crop are used to compute total kharif crop

water requirement for the village.

Crop Area under crop (ha) Crop water

requirement (mm)

Total crop water need

(TCM)

1

2

3

Total

Here all the crops which are under cultivation during kharif season are considered. This

includes traditional kharif crops like kharif jowar, bajra, soybean etc., the kharif vegetable

crops like tomato, onion etc. the long kharif crops like cotton, tur etc. as well as annual /

horticulture crops like pomegranate, sugarcane, banana etc.

Here the total crop water requirement of long kharif crops as well as annual crops is

considered. This has been kept so for the simplicity of calculations at the village level by

krushi sahayaks.

In reality, only one-third of the total crop water requirement for the annual crops and half

the requirement of the long kharif crops should be counted during kharif season and the

rest should be counted in the rabi season crop water requirement i.e. part 10 below.

6. Protective irrigation requirement

Protective irrigation requirement ideally would come from the farm level water balance and

from the crop water deficit. But in the JYS budget, as farm level balance is not computed, it

is assumed that due to long dry spells during monsoon season, there will be a deficit of at

least 10% of the kharif crop requirement.

Thus, protective irrigation requirement = 0.10 x Total kharif crop water requirement

7. Kharif protective irrigation water balance

34

The protective irrigation demand estimated in the part 6. is to be made available during

kharif season at different locations. For this, first it is checked whether existing water

conservation structures are enough to supply this amount.

a. Total runoff impounded by existing water conservation structures – from 3.

b. Total protective irrigation demand during kharif dry spells – from 7.

c. Extra runoff to be impounded to satisfy protective irrigation demand – (b – a)

Now if b. is greater than a., then (b – a) is the extra runoff which needs to be impounded by

new water conservation structures to satisfy protective irrigation demand during kharif

season. In case (b – a) is zero or negative, it means that the protective irrigation demand is

already satisfied.

Care needs to be taken here that there are enough water pockets in the poor soil areas,

because these are the areas where the protective irrigation demand will be more.

8. Evaporation from non agricultural lands

In many villages, area under waste lands, fallow lands or forest cover is substantial. In this

case, the evaporation or evapo-transpiration occurring in these lands is also substantial and

contributes to overall water balance. Hence these need to be considered.

The evaporation from non-vegetative fallow lands is minimal where water is lost only

through soil evaporation which is of the order of around 50-60 mm during the whole

monsoon season. The evaporation or evapo-transpiration occurring from small shrubs,

grass, etc. can be considered up to 200 mm per season whereas the evapo-transpiration

from the thickly forested areas (i.e. dry tropical forests) can be considered as more than

800mm per year. For simplicity following figures are considered.

Land type Area (ha)

Evaporation / Evapotranspiration demand (mm)

Total water lost to atmosphere (TCM)

Fallow land or current fallow

50

Shrub forests or grasslands

200

Thickly forested area 800

Total

9. Total water available at the start of rabi and summer season

Now that all the outgoing components till kharif season are computed, we can compute the

total water available at the end of kharif season, which would be available for the coming

rabi and summer seasons.

35

Thus,

In this case, as we have already considered the total requirement of long kharif and annual

crops, this water is available for new sowing of crops in rabi and summer seasons.

10. Rabi and summer crop water requirement

Rabi and summer crop water requirement is computed just as the kharif crop water

requirement in part 5.

Here, the crops and area under crops can be futuristic i.e. the planned rabi sowing or can be

taken from past records for the similar rainfall pattern.

Crop Area under crop (ha) Crop water

requirement (mm)

Total crop water need

(TCM)

1

2

3

Total

11. Water available at the end of rabi and summer season

The crop water requirement for rabi and summer season is compared with the total water

available at the end of kharif season. If this amount is more, i.e. requirement more than

availability, then the difference is either the amount falling short during rabi and summer

seasons or is brought by farmers from outside the system. Outside the system in this case

can mean outside the village (i.e. lifting water from far distances or from irrigation canal

coming from outside village) or from deep borewells which tap very deep aquifers (i.e. more

than 100-200 feet).

The negative quantity here means that the current cropping pattern is not sustainable if

only the water available from rainfall is considered.

36

12. Rabi water use index

If this index is greater than 1, it means the situation is unsustainable.

This either means that more runoff needs to be impounded in order to increase the supply

side, or the demand needs to be regulated.

37

Appendix II

गाव पाणलोट आराखडा

पाण्याचा ताळेबंद – नमनुा (मरहळ ख.ु, नाशिक)

१. पर्जन्यमानाने उपलब्ध होणारे पाणी १.१ पर्जन्यमान : ३८१ मम.मम. १.२ पाणलोट क्षेत्र : ५४४.२६ हे.

१.३ उपलब्ध होणारे पाणी = पाणलोट क्षेत्र हे पर्जन्यमान मम मम

१०० टी.सी.एम.

= ५४४ २६ ३८११०० टी.सी.एम.

= २०७३.६३ टी.सी.एम. २. पर्जन्यामानामुळे शमळणारा अपधाव (स्ट्रेंर् तक्ता आधारे) प्रपत्र क्र ३.१ – ५ टक्के पेक्षा कमी उतार असलेल्या पाणलोट क्षेत्रासाठी प्रपत्र क्र ३.२ – ५ ते २० टक्के उतार असलेल्या पाणलोट क्षेत्रासाठी प्रपत्र क्र ३.३ – २० टक्के पेक्षा अधधक उतार असलेल्या पाणलोट क्षेत्रासाठी २.१ अपधाव काढणे – अ. क्र. पाणलोटाचा प्रकार क्षेत्र (हे.) प्रतत हे. अपधाव

(टी.सी.एम.) एकुण अपधाव (टी.सी.एम.)

१ उतार २० टक्के पेक्षा अधधक २४३ ०.४२९८ १०४.४४

२ उतार ५ त े२० टक्के १३५ ०.३३०१ ४४.५६

३ उतार ५ टक्के पेक्षा कमी १६६.२४ ०.२१३४ ३५.४७

एकुण १८४.४७

38

३. मदृ व र्ल संधारण कामांमुळे होणारे पुनर्जरण

अ.क्र.

कामाच ेनाव संख्या / हे.

बाष्पीभवन (%)

उवजररत उपलब्ध पाणी (%)

एकुण साठवण क्षमता (टी.सी.एम)

पावसाळ्यातील

एकुण भरण संख्या

एकुण उपलब्ध होणारे पाणी (टी.सी.एम)

(१) (२) (३) (४) (५) =

१०० – (४) (६) (७) (८) =

(६)x(५)/१००x(७) १ सलग

समतल चर, खोल सलग समतल चर

२ कंपाटजमेंट बंडडगं

३५ ५०%

५०% १५.९२ २ १५.९२

३ ढाळीच े बांध बंदिस्ट्ती

-- -- --

४ मर्गी

५ शेत-तळे (no plastic)

३ ५०% ५०% ६.३ २ ६.३

६ बोडी

७ माती नाला बांध

३ ३०% ७०% १२ २ १६.८

८ सीमेंट नाला बांध (खोलीकरण)

२ ३०%

७०%

१४ २ ९.६

ल पा र्लसंधारण

९ सीमेंट नाला बांध

३ ३०%

७०% १७ २ २३.८

१० पाझर तलाव १ ५०% ५०% २० १ १४

ल. पा. जर्.प.

११ के. टी. वेअर िरुूस्ट्ती

१ ५०% ५०% २० २ २०

१२ पाझर तलाव िरुुस्ट्ती

१ ५०%

५०%

२५ १ १२.५

एकुण ११८.९२

पाझर तलाव, कोल्हापूर पद्धत बंधारा, साठवण तलाव, मसचंन तलाव

या सवज साठवण योर्नांबाबत लघु पाटबंधारे संदहतमेधील (M.I. Manual) मागजिशजक सूचनांप्रमाणे ववद्यमान पररस्स्ट्ितीत ज्याप्रमाणे येवा काढणे व मोर्माप केले र्ात ेत्याप्रमाणे ककंवा सद्यस्स्ट्ितीत र्ी अद्ययावत केलेली पद्धत वापरून येवा, पाणी साठा व मसचंन क्षमता काढल्या र्ात ेव प्रकल्प अहवालास मान्यता ममळते.

39

४. पपण्याच्या पाण्याची एकुण गरर् अ. क्र.

बाब सखं्या आवश्यक पाणी प्रतत दिन (मलटर)

एकुण आवश्यक पाणी (वावषजक) (टी.सी.एम)

(१) (२) (३) (४) (५) = (३) x (४) x ३६५ / १०,०००००

१ माणस े ७११ ५५ मलटर १४.२७

२ र्नावरे २०१ ३५ मलटर २.५६

३ शळे्या – मेंढ्या १४०० ५ मलटर २.५५

४ कुक्कुट पालन -- २ मलटर -- एकुण १९.३८

५. खरीप हंगामातील पपकांसाठी पाण्याची गरर् र्ल व भूमी व्यवस्ट्िापन संस्ट्िा औरंगाबाि (WALMI) या संस्ट्िेकडील पुस्ट्तीकेनुसार हवामान तनहाय प्रमुख वपकांच्या पाण्याची गरर् आधारे पाणलोटातील सद्यस्स्ट्ितीतील खरीप हंगामातील लागवडी खालील असलेल्या सवज वपकांच्या उपलब्ध क्षेत्राच्या आकडवेारीच्या आधारे पाण्याची गरर् काढण्यात यावी. ५.१ खरीप हंगामातील प्रमुख वपके अ.क्र. वपकाचे नाव क्षेत्र (हे.)

आवश्यक पाणी प्रतत हे. (मम.मम)

एकुण आवश्यक पाणी (टी.सी.एम.)

(१) (२) (३) (४) ३ ४ १००

१ बार्री २६५ ३०० ७९५

२ मगु ५ २५० १२.५०

३ सोयाबीन १५ ३५० ५२.५०

४ मका २५ ४०० १०.००

५ तरू ५ ५७५ २८.७५

६ चारा वपके ३ ३०० ९.००

एकुण ३१८ ९०७.७५

40

५.२ खरीप हंगामातील नगिी वपके अ.क्र. वपकाचे नाव क्षेत्र (हे.)

आवश्यक पाणी प्रतत हे. (मम.मम)

एकुण आवश्यक पाणी (टी.सी.एम.)

(१) (२) (३) (४) ३ ४ १००

१ कापसू १० ८५० ८५

२ - - - - एकुण १० ८५

५.३ खरीप नगिी वपके अ.क्र. वपकाचे नाव क्षेत्र

(हे.)

आवश्यक पाणी प्रतत हे. (मम.मम)

एकुण आवश्यक पाणी (टी.सी.एम.)

(१) (२) (३) (४) ३ ४ १००

१ ....

एकुण

५.४ वावषजक वपके (फळ वपके / उस) अ.क्र. वपकाचे नाव क्षेत्र

(हे.)

आवश्यक पाणी प्रतत हे. (मम.मम)

एकुण आवश्यक पाणी (टी.सी.एम.)

(१) (२) (३) (४) ३ ४ १००

१ डामळंब १ १२०० १२

२ - - - - ३ - - - -

एकुण १२

खरीप हंगामासाठी वपकांना लागणाऱ्या पाण्याची एकुण गरर् = ५.१) + ५.२) + ५.३) + ५.४) = ९०७.७५ + ८५ + ० + १२ = १००४.७५ (टी.सी.एम.)

41

६. खरीप हंगामात संरक्षित शसचंनासाठी आवश्यक पाणी साठा

संरक्षक्षत मसचंनासाठी आवश्यक

पाणीसाठा (टी.सी.एम) = ०.१ x खरीप हंगामातील

वपकांची पाण्याची गरर् (टी.सी.एम)

= ०.१ x १००४.७५

= १००.४७ टी.सी.एम.

७. खरीप हंगामासाठी पाण्याचा ताळेबंद

अ) अस्स्ट्तत्वातील मिृ व र्ल संधारण कामांमुळे

उपलब्ध होणारे पाणी -- ११८.९२ टी.सी.एम.

ब) खरीप हंगामात संरक्षक्षत मसचंनासाठी

पाण्याची गरर् -- १००.४७ टी.सी.एम.

क) खरीप हंगामाशवेटी र्ल-संधारण कामांमुळे

अततररक्त पाणी साठा अ) – ब) -- +१८.४५ टी.सी.एम.

८. बबगर ितेी र्शमनीतून होणारे पाण्याच ेबाष्पीर्वन (वन-िेत्र, कुरण/गवत व पडिेत्र)

अ.क्र. र्ममनीचा प्रकार क्षेत्र (हे.) पाण्याचे बाष्पीभवन (मम.मम.)

एकुण पाण्याच ेबाष्पीभवन

(टी.सी.एम.) (१) (२) (३) (४) (३)x(४)/१०० १ कायम पड / चाल ूपड / बबगर

शतेी १४७.१ ५० ७३.५५

२ कुरण / गवत / गायरान १७.२ २०० ३४.४

३ वन क्षेत्र ० ८०० ०

एकुण १०७.९५

42

९. रब्बी व उन्हाळी हंगामासाठी शिल्लक पाणी

रब्बी व उन्हाळी हंगामासाठी उपलब्ध पाणी टी सी एम

पर्जन्यमानातून उपलब्ध होणारे पाणी मुद्दा क्र १ नुसार पर्जन्यामानामुळे होणारा अपधाव मुद्दा क्र २ नुसार वपण्याच्या पाण्याची गरर् मुद्दा क्र ४ नुसार खरीप हंगामातील लागवडीखालील वपकांची गरर् मुद्दा क्र ५ नुसार बबगर शतेी र्ममनीतून होणारे पाण्याच ेबाष्पीभवन मुद्दा क्र ८ नुसार खरीप हंगामातील संरक्षक्षत मसचंनासाठी पाण्याची गरर् मुद्दा क्र ६ नुसार मिृ व र्ल संधारण कामांमुळे उपलब्ध होणारे पाणी मुद्दा क्र ३ नसुार

रब्बी व उन्हाळी हंगामासाठी उपलब्ध पाणी टी सी एम

२०७६ ६३ १८४ ४७ १९ ३८ १००४ ७५ १०७ ९५ १०० ४७ ११८ ९२

= ७७५.५३ टी.सी.एम.

१०. रब्बी व उन्हाळी हंगामातील पपकांच्या पाण्याची गरर्

१०.१ रब्बी हंगामातील प्रमुख वपके

अ.क्र. वपकाचे नाव क्षेत्र (हे.)

आवश्यक पाणी प्रतत हे. (मम.मम)

एकुण आवश्यक पाणी (टी.सी.एम.)

(१) (२) (३) २ ३ १००

१ गहू १५ ५५० ८२.५०

२ हरभरा १० ३०० ३०.०० ३ र. ज्वारी ३० ४७५ १४२.५० ४ गळीत धान्य २५ ४५० ११२.५० ५ मका ५ ४०० २० ६ चारा वपके ५ ४०० २०

एकुण ९० ४०७.५०

१०.२ रब्बी हंगामातील भार्ीपाला वपके

अ.क्र. वपकाचे नाव क्षेत्र (हे.)

आवश्यक पाणी प्रतत हे. (मम.मम)

एकुण आवश्यक पाणी (टी.सी.एम.)

(१) (२) (३) २ ३ १००

१ कांिा २० ६५० १३०.००

43

२ टोमेटो ५ ६५० ३२.५० एकुण २५ १६२.५०

१०.३ उन्हाळी हंगामातील वपके

अ.क्र. वपकाचे नाव क्षेत्र (हे.)

आवश्यक पाणी प्रतत हे. (मम.मम)

एकुण आवश्यक पाणी (टी.सी.एम.)

(१) (२) (३) २ ३ १००

१ भईुमगु २ ७५० १५.००

२ चारा वपके २ ४०० ८.०० ३ -- -- -- --

एकुण ४ २३

रब्बी व उन्हाळी हंगामातील पपकांच्या

पाण्याची एकुण गरर् = (१०.१) + (१०.२) + (१०.३)

= ५९३.०० टी.सी.एम.

११. रब्बी व उन्हाळी हंगामाच्या िवेटी शिल्लक पाणी

रब्बी व उन्हाळी हंगामाच्या शवेटी मशल्लक पाणी रब्बी व उन्हाळी हंगामाच्या सुरुवातीला उपलब्ध पाणी मुद्दा क्र ९ नुसार रब्बी व उन्हाळी हंगामातील वपकांच्या पाण्याची गरर् मुद्दा क्र १० नुसार

= ७७५.५३ – ५९३.००

= +१८२.५३ टी.सी.एम.

१२. रब्बी र्ल-वापर ननदेिांक

= रब्बी व उन्हाळी हंगामातील वपकांच्या पाण्याची गरर्रब्बी व उन्हाळी हंगामासाठी मशल्लक पाणी

= ५९३ ०० टी सी एम

७७५ ५३ टी सी एम

= ०.७६४

44

तनष्कषज

रब्बी र्ल-वापर तनिेशांक हा

अ) १.० पेक्षा कमी आल्यास -- सुरक्षित जथिती ब) १.० पेक्षा र्ास्ट्त आल्यास -- असुरक्षक्षत स्स्ट्िती

१३. कृती आराखडा

वरील पाण्याचा ताळेबंि व MRSAC आणण GSDA नी बनववलेल्या नकाशांच्या आधारे गाव पाणलोटामध्ये घ्यावयाची नवीन मिृ व र्ल संधारणाची कामे तनस्श्चत करण्यात यावीत व त्यानुसार कृती आराखडा बनववण्यात यावा.

वरील प्रमाणे कृती आरखडा बनववताना खालील प्रमुख उदद्दष्टे लक्षात घ्यावीत. प्रपत्र ब) “पाण्याचा ताळेबंि तयार करण्यासाठी मागजिशजक सूचना” या मध्ये खालील उद्दीष्टान्ची अधधक मादहती िेण्यात आली आहे.

खरीपातील संरक्षक्षत मसचंनाची गरर् पुरववणे

रब्बीतील लागवडीखालील क्षेत्र वाढववणे

खरीपाखालील क्षेत्र वाढववणे

रब्बी र्ल-वापर तनिेशांक आटोक्यात आणणे

वन क्षेत्र व उवजररत बबगर शतेी र्ममनीवर मिृ संधारणाची कामे करणे

वपण्याच्या पाण्याची बारा मदहने सवाांना उपलब्धता करणे