Created by Dottie Depperschmidt;

1. Water: Is there enough ? The water supply available to farmers in the West is declining. Many aquifers are being depleted faster than they can be recharged, and more surface water is being diverted to cities and industry rather than to agricultural uses. Ground water levels affect stream flow because in many cases, the elevation of a water table of an area surrounding a river influences the elevation of water in the river. As new wells are drilled and pumped, they lower the water table in the ground and the water level in the stream. The result of this is newer agricultural wells are being shut down to preserve senior water rights on other wells or rivers. The effect of lower stream flow is that downstream water users are challenging upstream users for their full allotments. In addition, the pressure of fish habitat protection and other environmental impacts that require higher stream levels are causing farmers to see a decrease in the water that is flowing to their farms. Center Pivots Use Less Water than Furrow Irrigation Weather Station for Monitoring Crop Water Needs Remote sensing for Crop Nitrogen Status Furrow-irrigation induced erosion Created by Dottie Depperschmidt; Content developed by Mathew Stocktonfor his Colorado Statue University class , Writing the Sciences, Fall, 2006;

2. WMR’s New Research Direction Will Address These Limited Water Issues: WMR’s newest research project will address agricultural issues in sustaining crop production with decreasing water supplies in the Great Plains. This project is expected to take place over the next five years, with research being conducted on farmland in eastern Colorado. The research team consists of five scientists with extensive backgrounds in soils, plants, water and weed management. Dr. Walter Bausch, Ag. Engineer specializing in ground-based remote sensing of crop water and N status; Dr. Gerald Buchleiter, Ag. Engineer specializing in irrigation water scheduling and crop water demand; Dr. Dale Shaner, Weed Physiologist specializing in herbicide behavior in the plant and in the environment; Dr. Thomas Trout, Ag. Engineer and WMR Research Leader specializing in irrigation management practices and erosion in surface irrigation systems; and Dr. Lori Wiles, Weed Ecologist specializing in weed population dynamics and ecology. • The Primary Agricultural Issue In The Great Plains Is The Sustainability Of Irrigated Agriculture With Declining Water Supplies. • Irrigated Agriculture is critical to our food supply (40% of crop value; grains and forages for beef and dairy); important to rural economies; impacts arid ecosystems; and facing declining water supplies. Census of Agriculture 2002. National Agricultural Statistics Service • As an Example: The State of Colorado • SWSI 2004-inventory of existing Colorado water uses and projected needs for next 25 years. Colorado Water Conservation Board. Statewide Water Supply Initiative Report .(SWSI) November 2004. • Currently: • Statewide 3.1 M acres with 1.0 M acres in South Platte (NE Colorado) • Ave. annual shortages of >10% for Eastern Slope (DWR data) • In 2030: • 65% increase in population (2.8 M) with 86% living on Eastern Slope • 53% increase in Municipal & Industry (M&I) demand (630,000 acre-feet) after conservation practices • >20% shortfall … if all planned projects are developed. • Major Colorado Concerns • Transfer of agricultural water supplies to municipal uses • Colorado Big Thompson project – 50 years ago nearly 100% agriculture use. Currently 50% agriculture, 50% municipal and industrial. NCWCD Water Conservation & Management Plan. • Interaction between surface diversions and wells in “tributary” aquifers • State Engineer shut down 400 wells along the S. Platte in 2006 Hal Simpson. Sept. 2006. History of well regulation in South Platte River Basin. • Depletions of large aquifers e.g. Ogallala and Denver • Reduced well discharge; increased pumping costs Western Aquifers under Stress. Geotimes, May 2004. American Geological institute. • Interstate compacts • Litigation on Arkansas & Republican Rivers-curtail irrigation Interstate Water Allocation The WMR’s Plan of Action There are three main objectives that the WMR wants to achieve in the next five years, collectively focusing on sustainable crop production with limited water supplies in irrigated crop production. The research will focus on four crops- corn, sunflowers, wheat, and dry beans, grown under two tillage practices, conventional, and minimum tillage.

3. WMR Research Objectives Objective 1: Develop water production functions, weed management strategies, and remotely sensed water deficit measurements. The first goal is to refine crop water production functions for the 4 crops. A water production function is a measurement that relates a unit of crop production to a unit of water. These functions help predict water use per unit of crop produced and will be used to maximize crop production per unit of water used. A second goal of this objective is to understand the effects of different levels of irrigation on weed ecology and herbicide efficacy and dissipation. Finally, new land-based remote sensing tools for in-season water and nitrogen management will be researched.. By developing new strategies, the WMR hopes to create guidelines for several important aspects of irrigated agriculture with limited water supplies: water and N management, tillage, weed population and dynamics, and herbicide efficiency. Objective 2: Develop tools and strategies for site-specific weed management (SSWM). The WMR scientists will use field measurements as well as computer simulations to determine the effectiveness of weed management practices at specific locations on farmer’s fields. With this information, the scientists can gain more knowledge about SSWM, and how it can be applied to individual farms and fields. In SSWM you determine where weed patches are located in a field and then concentrate your control efforts in those areas. The benefit of SSWM over uniform management practices is that herbicides can be applied to smaller areas, thus reducing costs through lowered fuel and herbicide usage. As an example, utilizing SSWM, weeds will be controlled only where they occur, reducing herbicide application, while maintaining effective weed management and crop yield. Objective 3: Develop tools to assess the impacts of cropping systems and irrigation practices on furrow irrigation-induced erosion. The third objective of this research project is to assess the effects of crops and irrigation on furrow-irrigation induced erosion. Furrows are the small channels or ditches between two rows of plants used to run irrigation water. These small channels sometimes erode and good soil is carried off the field to rivers and lakes. Irrigation-induced erosion is difficult to predict because of the many soil, irrigation, and field factors. The WMR will participate in an ARS-wide effort to create a computer model that will predict the effects of different management practices on furrow-irrigation induced erosion. This coordinated research effort is in direct response to a Natural Resources Conservation Service (NRCS) request for a scientifically based irrigation induced erosion assessment tool that would help design conservation plans that reduce erosion (WMR Project Plan 2006). In Conclusion: All of these objectives tie into the main goal of WMR, to help farmers be self-sustaining in water limited areas. This research will help balance weed and crop growth under limited-irrigation conditions, while still allowing farmers to remain economically productive. With water supplies shifting towards city and industrial uses, farmers are experiencing a shortage of agricultural water. WMR is developing solutions to help irrigated agriculture remain sustainable.