Application of a spreadsheet model to groundwater use in the Mississippi Delta April 2016 David R. Johnson USACE-Vicksburg

Transcription

1 Application of a spreadsheet model to groundwater use in the Mississippi Delta April 2016 David R. Johnson USACE-Vicksburg

2 Issues How much water is being used for irrigation today? How much will be needed to irrigate all agricultural lands? How long will the existing groundwater last?

3 General Assumptions 1.5 Million Acres Currently Irrigated in the Delta 2.7 Million Acres is the Maximum Amount of Acreage that is Suitable for Irrigation in the Delta 30K New Irrigated Acres are Introduced each year (5 Year Average, YMD & NASS) 2.7 Million Irrigated Acres will be Reached in 2051

4 Sources of Irrigation Water Surface Water 185K Irrigated Agriculture Acres, or 12.3%, Use Surface Water for Irrigation Needs (2010 YMD Permit Data) Groundwater Primary Source of Irrigation Water 1,315K Irrigated Agriculture Acres, or 87.7%, Use Groundwater for Irrigation Needs (2010 YMD Permit Data)

5 Utilization of Irrigation Water Row Crops Water Needs are equal to the average water used per crop for the period 2002 through 2011

6 Methods of Irrigation Furrow Irrigation Primary Method of Irrigation in the MS Delta 1,155K Acres Currently Using Furrow Irrigation Average Water Need is 16 Inches/Acre Efficiency of 55% (Required Water/ Applied Water) Center Pivot Irrigation 300K Acres Currently Using Center Pivot Irrigation Average Water Need is 10.5 Inches/Acre Efficiency of 85% (Required Water/ Applied Water)

7 Utilization of Irrigation Water Fish Culture Currently <50K Acres of Catfish Requires 2 to 5 Feet/Acre Catfish Acreage Remained Constant Rice Production Currently 160K Acres of Rice in Production Requires 36 Inches/Acre (YMD 10 Year Average for Land Leveled Fields) Rice Acreage Increased by 0.5% a Year Over Previous Years Rice Acreage for Analysis

8 4,200,000 Status Quo Scenario Water Demand per Year (Acre-Ft) 4,000,000 3,800,000 3,600,000 Acre-Ft 3,400,000 3,200,000 3,000,000 Status Quo - Total Water Status Quo Status Quo - Deficit Irrigation 2,800,000 2,600,000 2,400,000 Initial Shows Groundwater Initial 900K 900K Acres & Surface Acres of of Soybeans Water Soybeans Soybean Withdrawals No Changes Soybean Acres are Made Acres Status Increase to the Increase Quo by Current by 15K System 15K Status Acres Acres Quo per per Year Year Center Pivot 2,200,000 Shows Groundwater Deficit Withdrawals New Irrigated Deficit is Acreage & Implemented All Phaucet New Irrigated is Added are at Implemented on 2% Acres of Soybean (30K/Year) 30K Acres per on Year 2% Acres of are Soybean per Irrigated Year Acres with per Center YearPivot No Changes 100% are of Made Soybean to Current Acres are System Irrigated with Deficit by 2066 Surface Water 100% Percentage of Maximum Soybean Remains Acres Center Constant are Pivot Irrigated Irrigated with Acres Deficit is & 1.2 Phaucet Million by (2041) ,000,000 New Irrigated Requires Requires Acreage 13 Requires 10.5 Inches/Acre is Inches/Acre Added 10.5 at Inches/Acre (69% 30K (86% Acres Efficient) Efficient) per (85% Year Efficient) Year Status Quo - Deficit Irrigation & Phaucet Status Quo - Center Pivot Status Quo Status Status Quo Deficit Irrigation Total Water Quo Deficit Irrigation & Phaucet

9 Model Calibration using the YMD annual change in aquifer volume YMD Fall to Fall Aquifer Volume Change

10 YMD fall to spring change in aquifer volume YMD Fall to Spring Aquifer Volume Change

11 YMD Fall to Spring change in aquifer volume versus mean winter precipitation (10 Stations) Mean Winter Precip Mean Winter Precip

12 YMD Fall to Spring change in aquifer volume versus mean stage of the Big Sunflower at Sunflower Sunflower Mean Elev (Oct-Mar) R² = Sunflower Linear (Sunflower) YMD volume changes are for the central Delta

13 YMD Summer change in aquifer volume YMD Spring to Fall Aquifer Volume Change

14 NASS Irrigated Acres in Mississippi Delta 70.00% 60.00% 50.00% 40.00% 30.00% Irrigated Crops Annual Est Linear (Irrigated Crops) y = x % 10.00% 0.00%

15 NASS irrigated crops by year with average water use per acre Estimated Irrigation Demand Rice

16 YMD Spring to Fall Volume Change versus CDD 0 Cooling Degree Days CDD Linear (CDD) R² =

17 25.00 Moorhead Mean Summer Temperature and Total Precipitation (Apr-Sep) 30.0 Moorhead T_Precip Mn_Temp

18 YMD Fall to Spring change in aquifer volume versus the calculated water demand 0 YMD Summer Deficit Versus the Calculated water demand using Evap - Precip R² = YMD Summer Deficit Linear (YMD Summer Deficit) Water Demand 20.5 in ET/year (Jun to Aug precip) * 55% efficiency for furrow and 3 ac-ft for rice

19 YMD water use by crop versus (ET irrigation season precipitation) 18 YMD Observed Use vs Predicted Cotton 16.5 R² = Corn 20.5 R² = Soy Beans 20.5 R² =

20 YMD Water Use by Crop ( ) Year Cotton Soybeans Corn Rice Aquaculture Ave AC-FT Ave Inches Irrigation Season Precipitation + Water Used Cotton Soy Beans Corn Irrigation Season Cotton and Soy Beans Jun-Aug Corn May-Jul

21 YMD annual change in aquifer volume versus estimated water use based on NASS crop acres and calculated irrigation demand Precipitation Adjusted Irrigation Estimate YMD Obs USACE

22 YMD Spring to Fall change in aquifer volume versus recharge adjusted estimate Recharge Adjusted Irrigation Estimate YMD Obs Recharge

23 Comparison of Acreages Million Acres Million Acres Surface Water Center Pivot Fish Culture Rice Furrow Irrigation Surface Water Center Pivot Fish Culture Rice Furrow Irrigation

24 3,800,000 Status Quo Scenario Groundwater Use per Year (Acre-Ft) 3,600,000 3,400,000 3,200,000 Acre-Ft 3,000,000 2,800,000 2,600,000 2,400,000 Status Quo Status Quo - Deficit & Phaucet Recharge Deficit, Phaucet, Recharge 10% Jason No Rice No Rice + Jason's 2,200,000 2,000,000 1,800, Year Jason s Suite Deficit, pipe planner, moisture meters and surge valves Alternate wetting and drying for rice

25 MAV Aquifer Volume sq mi acres depth % water ac-ft/foot ,224, ,480, ,224, ,600, ,224, ,720, ,224, ,720, est. 127,000, report to Governor stated 42% of aquifer has been used to date. 42%= 53,340,000 58% 73,660,000.00

26 80,000,000 70,000,000 Cumulative loss to ground water Total Irrigation use total recharge Approx. total remaining volume in the aquifer = 75 million acre-feet 60,000,000 50,000,000 40,000,000 30,000,000 20,000,000 Status Quo Deficit&PipeP Def_PP_FD Recharge 10%Jason No Rice No Rice+Jason New Regulation 10,000, ,000, inches/acre/year all crops -20,000, Calibrated by making the total deficit for the first 10 years equal to the observed loss

27 80,000,000 70,000,000 Cumulative loss to ground water Total Irrigation use total recharge Approx. total remaining volume in the aquifer = 75 million acre-feet 60,000,000 50,000,000 40,000, feet of screens 30,000, feet of screens 20,000,000 10,000, feet 0-10,000, inches/acre/year all crops -20,000, Status Quo Deficit&PipeP Def_PP_FD Recharge 10%Jason No Rice No Rice+Jason New Regulation Calibrated by making the total deficit for the first 10 years equal to the observed loss