Irrigation Efficiency Improvements: Technical,

Economic,and Policy Issues

NM Geological Society  NM Tech University, Socorro

Frank A. WardNMSU ACES

April 12, 2013

History of Water Use in Rio Grande• Why that history is important

– Identify history/culture– Uncover long term water supply trends– Piece together lessons for current drought/climate adaptation

• Data sources– Stream gauges since late 1800s (in and out of NM)– Historic tree ring analysis – Water delivery records of cities, towns, and other water

suppliers (e.g., Santa Fe, Albuquerque, LC).– Historic farm land in production– Historical Documents (3 better-known)

• Great River: The Rio Grande in NA History (P. Horgan, 1984)• Water in NM, A History of its Mgmt, Use (I. Clarke, 1987)• Historic Management of NM’s Acequias (Ackerly, 1996) 2

Acequias• A community-operated watercourse (canal,

ditch, ditch system,…).

• A publicly owned and operated irrigation facility.

• In northern NM, the oldest were established before 1600.

3

History: some high points• 1598 – north of Rio Chama Rio Grande confluence:

Onate build an acequia to irrigate crops (I Clark, 1987)• early 1600s – remarkably similar throughout the region

(Torquemado, 1609)• 1700 - 1800, more than 100 acequia systems built

(Dominguez).• 1752, Rio Grande below Albuquerque completely dry

(Humbolt, 1966).• 1855-7, European immigrants learned hard lessons

about the limits of crop growing without regular rainfall and streamflows (Davis, 1857).

• Licenses for land worth little without water. 4

More High Points

• 1891 (JW Powell)– Water control systems were limited by water,

inefficient, and temporary– about 15000 acres irrigated in Taos Valley – Only about 1/3 of land under the ditch actually tilled

(water limits land). – Also a problem in Afghanistan today.

5

Messages• Water supply limits (human) water use. • You can infer the history of water use in the Rio

Grande if you can estimate long term supplies. • Before modern large storage dams, pumps,

interbasin transfer projects, desalination technology, recycling and reuse, water in the river was the limiting resource

6

What did past water use in NM’s Rio Grande Basin look like?

7

Reconstructed Flows, Tree Rings, Rio Grande at Otowi Gauge (1450-2002)

8

Source, Treeflow: Woodhouse, Lukas, and Meko

http://treeflow.info/riogr/riograndeotowinatural.html

Historic RG Flows into NM (k-af/yr)USGS Stream Gauge Data – 3 hws

• Rio Grande at Del Norte (CO) – Flows = 657.93 – 109.17 post 2000 – 1891-2010 (110 years)

• Conejos River at Mogote (CO)– Flows = 238.59 – 49.16 post 2000– 1899-2010 (101 years)

• Rio Chama at Chamita (NM)– Flows = 438.14 –99.05 post 2000– 1970 – 2010 (41 years) 9

10

• Climate Change: more floods/droughts, greater conflict potential in dry places like NM

• Continued population and urban demand growth• Shrinking key ecological assets• Irrigated ag consumes 85-90% of water in NM• Ongoing search for ways to conserve water in

irrigated agriculture– technology (drip, sprinkler, water saving crops)– policy (subsidies, regulations, pricing,

… )– Projects (infrastructure, leveling, … )

Background

11

Reducing irrigation water use

• Reduce land in production– Cities buy or rent water or water rights from ag– Farm prices deteriorate

• Alter crop mix, e.g.:– More acres in cotton– Fewer acres in alfalfa, pecan orchards– Develop more drought tolerant crop varieties

• Reduce water application rates (deficit irrigate)

• Shift to water conserving irrigation technology– To sprinklers– To drip irrigation

ReminderEvaporation v Transpiration

Irrigation / AcWeighted Ave over Crops (EBID)

12

Technology

Apply ET E? T? I. Eff

Surface 4.27 2.74 0.64

Drip 3.45 3.16 0.90

Separating E from TZ. Samani, NMSU, April 3, 2013

• No simple methods for separating E and T. His satellite ET map of EBID does not split E-T.

13

14

Gaps• Little work in NM (or elsewhere) explaining

what affects irrigation water savings that integrates– Farm economics: profitability

– Farm hydrology: water application

– Agronomy: yields by crop

– Basin hydrology: net water depletions

– Basin institutions: protect senior water rights

15

Aims• Data: Assemble data on crop water

applications, crop water use, yields, land in production, crop mix, cost, and prices that characterize economics of irrigated ag in NM’s RG Project Area

• Economic analysis: Analyze profitability, production, land and water use in the Area.

• Policy Analysis: Forecast the same for:– Several drip irrigation subsidies 2– Selected water supply scenarios 6

16

Study Region: Elephant Butte Irrigation District

• http://www.ebid-nm.org/

17

Approach

• Analyze water conservation subsidies that reduces capital cost to convert from surface to drip. – Farm Income effect– Hydrologic effect on water app/depletion

• Integrates farm economics and basin hydrology

18

Farm Economics

• NMSU Farm costs and returns

• Published by NM county, year, crop, and irrigation technology

• Web -- http://aces.nmsu.edu/cropcosts/

Pecans, drip irrigated

19

Pecans, surface irrigated

20

Pecans: Drip or Surface Irrigated

21

22

Farm Water Economics 101

• Compare drip and surface irrigation– Drip: better applies quantity and timing of

water that the plant needs for max yields– Drip: higher yields higher ET, lower aquifer

recharge– Drip: reduces water applied– Drip: conversion costs are high

23

Cost of Converting:Surface to Drip Irrigation

• Conversion Capital Costs: – About $2500 / ac for 10 year life– About $365 / ac per year at 7% interest

• Conversion is a major investment, so for the conversion to increase income:– Yield gain must be high – or– $ Value of saved water must be high

24

• Basin-wide Evapotranspiration mapping

• Demand forecasting, water operations support

• Depletion changes with:– Management options

– Changing crops

– Drought cycles

• Informs sustainable water management

EBID Remote Sensing: NMSU

• Maximizes Farm Income by choosing land in production, by – crop – irrigation technology

• Subject to Constraints– Hydrologic (gw, sw)– Agronomic: yields, including salinity– Economic: Pecan acreage– Institutional25

Quantitative Analysis of NM Ag Water Conservation

26

Crop Water Data Used, EBID, NM (Samani)

Crop Tech

A ET RYield

ton/acTech

A ET RYield

ton/acac-ft/ac/yr ac-ft/ac/yr

Alfalfa S 5.0 3.3 1.7 8.00 D 4.1 3.7 0.4 9.00

Cotton S 3.0 2.3 0.7 0.42 D 2.8 2.5 0.3 0.46

Lettuce S 2.5 1.5 1.0 11.88 D 1.9 1.7 0.2 13.83

Onions S 4.0 2.3 0.7 16.88 D 3.0 2.7 0.3 20.08

Green Chile S 3.0 2.0 1.0 11.00 D 2.7 2.4 0.3 13.25

Red Chile S 3.0 2.0 1.0 1.75 D 2.5 2.2 0.3 1.95

Pecans S 5.0 3.0 2.0 0.58 D 4.1 3.7 0.4 0.72

27

Under the Hood

28

Max Irrigation Income

[ * ]uckt ct uckt uckt ucktInc P Yield Cost L

(1 )

( . )

ucktt

u c k t u

IncNPV Income

r

u location

c crop

k irrig tech surface v drip

t year

• EBID land: about 90 K acres • EBID area water price and supply

– SW = 4 – 6” 2013– GW = $90 per af pumped 2013

• Salinity impacts on yields• Institutional

– Endangered Species Act– Rio Grande Compact– US Mexico Treaty of 1906– Rio Grande Project operation agreement

(NM/TX)

• Water Rights Protection– No increase in water depletions: NM OSE29

Constraints

30

Results

31

Table 1. Economic Value of Depleted Water in Irrigation by Level of Supply and Source, Lower RG, USA, 2012 ($US/Ac-Ft Consumed)

sw_supply subsidyDepletions (k-ac-ft/yr) $US/a-f depletedsw gw tot sw gw

1-100_pct1-0 169 0 169 0 0

2-100 169 1 170 38 0

2-80_pct1-0 135 14 149 38 0

2-100 135 34 170 38 0

3-60_pct1-0 101 37 139 81 0

2-100 101 67 168 83 0

4-40_pct1-0 68 69 137 126 0

2-100 68 102 169 124 0

5-20_pct1-0 34 103 137 126 0

2-100 34 135 169 128 0

6-00_pct1-0 0 128 128 366 0

2-100 0 171 171 328 0

32

Lessons Learned: water- conserving technology

• Irrigators invest in water-saving technologies when faced with lower costs for converting from surface to drip.

• Drip irrigation subsidies farm income, crop yields, value of food production, and crop water applications.

• By raising crop yields and raising crop water ET, drip irrigation subsidies put upward pressure on water depletions.

• Where water rights exist, authorities need to guard against depletions with growing subsidies that reduce water applications.

• In RG Project Area, NM, the economic value of water is $126 - $128 per acre foot depleted with 20% of full surface supplies (e.g. 2013).

33

Research Questions• What policies would sustain NM’s aquifers affordably?

• What actions would reduce ag water use likely to occur?

– Without climate change

– With climate change that affects:• Yields

• Evaporation

• ET

• Supplies

– With high, medium, low future: • Prices

• Yields

• Costs

Tentative answers• Better water measurement

– Gauges– Tracking use by crop (application, ET)

• Better water accounting– Current use patterns– Potential use patterns

• Adjudications– Who has the senior/junior rights in the

face of future supply variability. Important as drought/climate intensifies.

– Can promote trading water for $ 34

Thank you

http://agecon.nmsu.edu/fward/water