Tackling Groundwater Problems in Arid and Semi Arid Regions:Debating Physical Options

M. Dinesh KumarInstitute for Resource Analysis and Policy

HyderabadEmail: dinesh@irapindia.org

Purpose of the Session

This session would discuss the various physical options for groundwater management in the context of semi arid and arid regions of India, and their scope and limitations.

Content

Introduction to overview of problems

Supply side options for groundwater management Scope and limitations

Demand side options for groundwater management Scope and limitations Technology and cropping systems

Introduction

Groundwater is an important water source in many dry regions of the world

Reasons are the large stocks, and reliability of supplies, as compared to highly variable nature of surface water sources

Largely treated as an inexhaustible source of water for a long time

Well irrigation has great advantages over surface irrigation

Introduction contd..

In Indian sub-continent, the resource is characterized by high physical heterogeneity

Unconsolidated formation (mainly alluvial) Semi-consolidated formations (sedimentary

sandstone Consolidated formations (hard rock formation of

basalt, crystalline rocks and sandstone origin)

Over-development is causing threat to groundwater supplies for irrigation and drinking uses in terms of depletion and quality deterioration in many regions

Introduction … contd.

A comprehensive understanding of the management alternatives--physical, economic, institutional, policy and legal--, are lacking.

It is more so for South Asian countries.

Water policy makers are aware of the need for groundwater management, but often not familiar with the range of physical, economic, legal and policy instruments for groundwater management and their potential implications.

Standard instruments for controlling exploitation of groundwater

Supply augmentation

Water rights in the form of well permits; volumetric use rights

Indirect charges through energy pricing

Direct regulation of drilling; pump sets

Virtual water trade

Need local runoff; otherwise inter-regional water transfer

Strong political system; institutional mechanisms needed

Farmers are major vote banks in India

Difficult to enforce in Indian context

Many arid & semi arid areas are exporting virtual water

Physical approaches for groundwater management

There are three different types of benefits that the society could accrue from a management intervention.

They are: economic benefits; ecological/environmental benefits; and livelihood benefits.

From societal point of view, a management decision would be sound, only if the aggregate of these benefits exceed the costs of proposed interventions.

The aggregate benefits are a sum of the economic benefits and all the positive externalities on the society associated with the environmental/ecological and livelihood benefits.

How over-exploitation occurs?

The negative consequences associated with groundwater over-exploitation are a result of net groundwater outflows exceeding the net inflows.

The outflows could include: groundwater draft; evapo-transpiration of groundwater from shallow aquifers (both anthropogenic); groundwater outflows into streams and natural drainage and sinks; and regional (lateral) groundwater flows.

The inflows include: natural recharge from precipitation (rainfall and snow); regional (lateral) groundwater inflows; recharge from natural water bodies such as lakes, ponds, tanks and river flows; and recharge from irrigation (both conveyance systems and irrigation water application in the field).

Contd..

The negative consequences could be: secular decline in water levels; seasonal water levels drops; intrusion of sea water in coastal aquifers; land subsidence; and deterioration of natural quality of groundwater due to leakages from saline aquifers as a result of hydraulic gradients, and geo-hydrochemical processes; and reduction in stream flows.

The approaches to manage groundwater should attempt: i] reducing the outflows that are the results of anthropogenic activities, which can be managed through human actions; and, ii] increasing the components of inflows that can be manipulated by human actions.

Various supply side approaches

Increasing the Inflows: Local water harvesting and recharging of

groundwater through: Spreading basin method

Dug well recharging (ASR)

Check dams

Injection wells

Induced recharge

Percolation tanks with recharge tube wells

Watershed management

Supply side approaches

Water transfers from water-rich regions for providing alternative sources of water supply

California CVP

North Gujarat receiving SSP waters

Recycling and recharge Waste stabilization ponds

Soil Aquifer Treatment (Israel)

Potential of local water harvesting and artificial recharge Groundwater depletion and water scarcity

mainly occur in arid and semi arid regions

Water harvesting does not work in semi arid and arid regions with:

Low annual runoff, high inter-annual variability; high potential evaporation; and when basins are “closed”

This is due to:

Poor hydrological opportunities for harvesting and poor reliability of water supply

Poor economic viability

-ive d/s impacts due to high degree of water development

What is the condition in India?

Rainfall is low in most agriculturally prosperous regions of India, which experience depletion problems

Rainfall variability is also high

Evaporation rates are very high

The basins in these regions are also “closed”

Physical approaches for demand management

Agricultural water demand management

Technological interventions

Cropping system change

Growing crops in regions with high water productivity due to climatic advantages

Potential impacts of micro-irrigation on groundwater use

Depends on three factors:

How much water could be saved using the technology at the field level

What farmers do with the saved water

What opportunities exist at the macro level for adoption of the technology

Constraints and opportunities in adoption of micro irrigation systems Farmers without independent source of water have least incentive to adopt MI systems

Area under crops that are most amenable to MI systems in terms of water saving benefits and income benefits are low in semi arid & arid regions—7.8 M ha in India

Negligible in the Indus basin area in Punjab & Haryana

Absence of limits on groundwater pumping and zero marginal cost of using it reduces the economic incentives for farmers having smaller holdings in good aquifer basins

In hard rock areas, well interference further reduces individual initiatives to save water in the aquifer

Constraints and Opportunities in adoption of micro irrigation systems

Small operational holding of farmers increases the unit capital and operating cost of MI system

Predominance of small & marginal farmers limits large-scale adoption of orchards having long gestation period

In areas where power supply limits water abstraction, especially for large farmers, farmers have least incentive to go for MI systems as it does not help them expand the area

In hard rock areas, with limited groundwater, farmers have high incentive to go for MI systems, as they could expand the area under the irrigated crops

Current geographical spread of adoption of MIS is a testimony to this

Opportunities for field level water saving

Field level water saving through MIS depends on agro-climate, type of MI technology, groundwater environment; crop type; and current irrigation practices

Real water saving at field level would be significant in arid and semi arid basins, with deep groundwater table, with drip irrigation used for row crops

Such areas include alluvial central Punjab, western Rajasthan and north Gujarat and deep water table areas of peninsular India

But, applied water saving is also likely to be negligible in the Ganges plains even if crops amenable to such systems exist in this region

Opportunities for field level water saving The reasons is low non-beneficial depletion of

water from soils under traditional method of irrigation

Real water saving would be further lower as the deep percolation would be fully recovered

The potential for water saving drip irrigation in India was estimated to be 5.9 m ha

The total reduction in crop water requirement due to this was estimated to be 44 BCM.

What is the likely impact of MI systems on aggregate water use at the regional level?

Often MI adoption is associated with changes in cropping system towards from traditional crops to high valued orchards--north Gujarat, Nalgonda, Jalgaon etc.

Hence water saving at the field level could be high

But, this can also lead to expansion in irrigated areas, particularly in situations where actual irrigated area is less than the cultivable area

In areas where MI system results in “saving in applied water” alone, aggregate impact would be greater depletion of water

In situations like Punjab, MI system adoption can lead to real water saving, but cropping system is not amenable

What is the likely impact of cropping system changes at regional level?

Many traditional crops and dairying in semi arid and arid regions have low water productivity

Replacement of traditional crops by high valued fruit crops can cut down water use even at the aggregate level due to:

Significant reductions in depleted water for a unit area

Absence of sufficient cultivable area to use up all the saved water at the farm level

But, many farming systems are complex. Crop residues form inputs for dairying in many areas.

Dairying yields high water productivity in Punjab, when compliments rice-wheat system

How far can it work in Indus and Yellow Basins? Replacing low water-efficient rice-wheat system will

disturb dairying

Importing fodder would increase the farming risks if done at a large scale

Large scale adoption of high valued fruit crops can lead to market crash, leading to major drops in water productivity itself

Also, extent to which crop shifts can take place at the regional level would be constrained by concerns of food security, and employment generation in agriculture

Punjab part of Indus basin and also north China plains (part of Yellow river basin) employs rural labour on large-scale; export food to water-rich regions

Improving the productivity of existing crops will have to get priority

Agro-climate impact on crop water productivity

In many basins, major variations in agro-climate exist spatially Indian Punjab (900 to 400 mm rainfall)

Climate can affect crop yields through solar radiation and temperature

It can also affect the evapo-transpiration (change in humidity, wind speed)

Soil conditions will have impact on crop yields

Hence, agro climate can have big impact on water productivity

In Narmada basin, wheat water productivity varied widely across 9 agro climatic sub-regions

Summary

The approaches for augmenting groundwater in over-exploited areas.

They include: groundwater recharge using local runoff; recharge using imported water; and, recharge using treated wastewater.

In arid and semi-arid regions, the hydrological opportunities, the reliability and economic viability of artificial recharge using local runoff would be generally very low.

The other two options are being practiced in developed countries, where the financial resources for such schemes are available in plenty, and the environmental value of improved groundwater environment are well recognized.

Summary

Another major approach being tried world over the world is water-efficient irrigation, to raise crop water productivity.

They cover: water-efficient micro irrigation devices; and efficient irrigation practices, including efficient conveyance systems.

Field level real water saving due to water-efficient irrigation devices depends on the crop type, climate, soils and geo-hydrological environment

Water-saving at the aggregate level would depend on a variety of socio-economic conditions including availability of extra land for cultivation; the availability of power supply vis-à-vis the amount of groundwater that can be abstracted

Summary Scope for agricultural water productivity improvement

through crop shifts at the regional level would be determined by a variety of socio-economic conditions such as the contribution of the existing cropping system to regional food security, the employment generation in rural areas, and the presence of market infrastructure for high valued crops.

But, in any case, the outcomes of water productivity improvement through crop shifts in terms of reduction in groundwater draft would also depend on the opportunities for farmers to expand the area under irrigation.

We have also demonstrated that in some regions, opportunities might exist for enhancing water productivity by taking climatic advantages

Heterogeneity in geo-hydrology

Will Water Harvesting and Local Recharging Benefit Water-Scarce Regions?

Figure X: Water Level Fluctuation in Wells in Fulzar, Ghelo River Basin

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Rainfall, mm Nr-Median Far-Median

Sr. No

Type of Recharge Structure

(Life in years)

Expected Active Life of

the System

Estimated Recharge Benefit(TCM)

Capital Cost of

the Structure

(in Lac Rs.)

Cost of the

Structure per m3 of

water(Rs/m3)

Annualized Cost*(Rs/m3)

1 Percolation Tank

10 2.0-225.0 1.55-71.00 20.0-193.0 2.00-19.30

2 Check Dam 5 1.0-2100.0 1.50-1050.0

73.0-290.0 14.60-58.0

3 Recharge Trench/Shaft/

3 1.0-1550.0 1.00-15.00 2.50-80.0 0.83-26.33

4 Sub-surface Dyke

5 2.0-11.5 7.30-17.70 158-455.0 31.60-91.00

Estimated Unit Cost of Artificial Recharge Structures Built under Pilot Scheme of CGWB

Effect of Watershed Interventions on Run-Off

Ghelo-Somnath Rainfall and Reservoir Inflows

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69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 1 3 5

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Water Productivity in Crops and Milk Production

7.75 8.05

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Paddy Wheat Milk ProductionWat

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Water productivity in crops and dairying in north Gujarat

Net WaterProductivity in Crops and Milk Production

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Vibrant dairy economy is a constraint to saving groundwater in north Gujarat

Milk Production and Aggregate Groundwater Use with WST

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CNV-Hisangabad CNV- J abalpur CNV-Narshinhpur J habua Hills Saputara Platue Malwal Plateau Nimar Plains Northern Hill

Region of

Chhattisgarh

Vindhya Plateau

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Water productivity (Drought) Water productivity (Normal)

Water productivity in wheat in different regions of narmada basin

Current scale of adoption of MI systems

Name ofStates

Area underTotal

Area (ha)Drip SprinklerRajasthan 17002 706813 723815Maharashtra 482341 214674 697015Haryana 7136 518367 525502Andhra Pradesh 363073 200950 564023Karnataka 177326 228621 405947Gujarat 169689 136284 305973Tamil Nadu 131335 27186 158521West Bengal 146 150031 150177Madhya Pradesh 20432 117685 138117Chhattisgarh 3648 59270 62919Orissa 3629 23466 27095Uttar Pradesh 10675 10589 21264Punjab 11730 10511 22241Kerala 14119 2516 16635Sikkim 80 10030 10110Bihar 163 206 369Others 15000 30000 45000India Total 1429404 2452680 3882084