Conjunctive Management of Surface and Ground Water in Dawson and Buffalo Counties

1. Conjunctive Management of Surface and Ground Waterin Dawson and Buffalo Counties Sponsors Study Area

2. The development of ground water and surface water irrigation has provided positive benefits for the Central Platte valley Introduction

3. Introduction Nebraska ranks second among the states with respect to the area of irrigated acreage and the quantity of water used for irrigation.

4. Introduction The irrigation water comes from both ground and surface water sources. Study Area Dots are irrigation wells

5. Introduction The use of both ground water and surface water for irrigation in Nebraska has resulted in significant changes in ground water levels Study Area Source: 2002 US Geological Circular 1139

6. Study Area Irrigation Surface Water • 7 irrigation canals • 60,000 acres • 230,000 AF average annual diversion Ground Water • 2,900 wells • 120,000 acres ground water irrigated • Ground water also used to supplement surface water

7. Study Area Irrigation Map of Surface and Ground Water Irrigation Study Area Dots are irrigation wells

8. Study Area Problem • Relationship of surface water delivery and ground water recharge • Numerous ground water wells in Study Area benefit • Surface water recharges aquifer and prevents degradation of ground quality – nitrates • Ground water mining prevented • Changes in surface water delivery could change this balance • Parts of Study Area are declared over-appropriated by NDNR • Temporarily limits the development of new wells

9. Benefits of Conjunctive Mgmt Potential Beneficiaries of Conjunctive Management: • Ground Water Irrigators • Surface Water Irrigators • Municipal & Industrial Water Users

10. Benefits of Conjunctive Mgmt • Maintain ground water levels • Seepage from canals benefits ground water levels • Helps prevent increases in pumping costs • 1992 study – hypothetical impacts of reduced seepage • Examined area north of the Platte from Brady to Kearney • Explored the potential impacts of canal lining and increasing irrigation efficiency • Water table declines averaged > 7 feet over the long term (47 yrs) • Estimated long-term increase in pumping costs averaged $2.16 per acre per year • Max declines of 22 ft and pumping cost increase of $6.60/ac/yr

11. Benefits of Conjunctive Mgmt • Modeled potential ground water declines from canal lining and on-farm irrigation efficiency improvements

12. Benefits of Conjunctive Mgmt • Maintain ground water quality • Seepage tends to “flush” nitrates from ground water • Impacts of upsetting the balance between ground water and surface water • 1992 study – if recharge from canals and on-farm deep percolation decreased, could result in significant increases in nitrates if proper management is not instituted • Agricultural impacts – ground water management program requirements • Municipal impacts – new wells, drinking water treatment, etc.

13. Benefits of Conjunctive Mgmt • Current nitrate concentrations in ground water

14. Benefits of Conjunctive Mgmt • Keep the water in the Study Area • Study Area water supply impacts • Surface water use – net gains • Ground water use – net reductions • Need balance • Other users benefit if Study Area water rights are cancelled

15. Conjunctive Management Program • NPPD, CPNRD, and NDNR effort • Study, develop, and implement a conjunctive surface and ground water management program. • Optimize the total water supply • Sustain the surface water delivery system • Manage for surface and ground water quality • Public Involvement • Program development • Education • Phased approach

16. Conjunctive Management Study Overall Objectives: • Study, develop, and implement a conjunctive surface and ground water management program. • Inform and educate the public • Surface and ground water resources of the Central Platte valley • Effects and impacts on the people and natural resources.

17. Conjunctive Management Study Specific Objectives: • Develop comprehensive conjunctive surface and ground water management plan • Optimize the total water supply and manage for both surface and ground water quality • Sustain the surface water delivery system • Recharge benefits • Water quality benefits • Return flow benefits

18. Conjunctive Management Study Specific Objectives: • Study how surface and ground water compliment each other now and in the future • Account for existing water budget • Study costs of providing surface water • Propose alternatives for offsetting those costs • Analyze social & political environment • Evaluate alternatives for implementing conjunctive management • Phased approach for study

19. Conjunctive Management Program • Phase I: Data collection and evaluation • 2004 – 2005 • Decision to proceed to Phase II • Phase II: Plan development • 2005 – 2007 • Decision to proceed to Phase III • Phase III: Plan implementation • 2007 and beyond

20. Questions?