SDC341: Irrigation Management for Humid and Sub-Humid Areas
Statement of Issues and Justification
Irrigated agriculture continues to increase rapidly across the Southeast United States. Competition for limited water resources is one of the most critical issues being faced by irrigated agriculture in the United States and this is especially true for the Southeast. It has been the common belief that there is plenty of available water to meet the water needs but that has been brought into question as issues arise across the region. The partial examples that follow illustrate the issues that Southeastern States are facing.Governors of Alabama, Florida and Georgia scheduled to announce whether they have reached a negotiated settlement to their 17-year water war. They missed this deadline.
Trans-boundary water rights issues are also being debated between South Carolina and its North Carolina and Georgia neighbors, while news reads North Carolina's attorney general balks at secret water talks with South Carolina.
Corps of Engineers South Atlantic Region Commander Brig. Gen. Joseph Schroedel will convene a 16-state workshop to discuss creation of a water council to solve the southeast U.S. water sharing issues.
Georgia governor, lieutenant governor and House speaker appoint 300 farmers, government officials, businessmen and others to 10 regional councils to allocate water from the state's rivers, lakes and aquifers.
Southeastern United States experience drought conditions on a regular basis. Irrigation is becoming much more common as a means of risk reduction as well as a means of stabilizing or improving income. Surface water as well as ground water is utilized as a source of irrigation water. See http://www.drought.unl.edu/dm/monitor.html for map.
Recent drought in many areas has heightened the need to balance water demand with the available supply while ensuring the minimum in-stream flow requirements to meet human and environmental needs. The 13 Southern Region states are challenged to maintain an available, high-quality water supply in a region encompassing 19 million irrigated acres.
Ground-water depletion has been a concern in the Southwest and High Plains for many years, but increased demands on our ground-water resources have overstressed aquifers in many areas of the Nation, not just in arid regions. In addition, ground-water depletion occurs at scales ranging from a single well to aquifer systems underlying several states. The extents of the resulting effects depend on several factors including pumpage and natural discharge rates, physical properties of the aquifer, and natural and human-induced recharge rates
Conservation officials have declared 11 counties in Arkansas as critical groundwater decline areas and 21 more counties are under evaluation. In areas where subsidence has been attributed to ground-water pumpage. See http://water.usgs.gov/ogw/pubs/fs00165/SubsidenceFS.v7.PDF for map.
2009, South Carolina Senate introduced a bill (S. 452) to amend their 1976 Code relating to surface water withdrawal and reporting. This is expected to alter rights and exceptions and may impact irrigation water withdrawals during periods of drought when minimal stream flow requirements are not met.
Arkansas Ground Water Protection and Management Report for 2009 Irrigated acres are declining in the arid western states while continuing to increase in the Southeast. The blue areas on the left represent increasing irrigation while the red areas show declining irrigated acres over the period of 2002 to 2007. See http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/ Ag_Atlas_Maps/Farms/Land_in_Farms_and_Land_Use/ 07-M081-RGBDot2-largetext.pdf for maps
Much of what we know about irrigation was developed in areas where rainfall is minimal. The applicability of such results to the humid and sub-humid region is still in question. We continue to apply technology and develop solutions based on technology and concepts that may not be applicable to the area and in most cases do not include analysis of all available options. The illustration to the right shows the availability of freshwater. Blue and green areas have developed more than 100% of the available water while the yellow area (eastern US) is utilizing less than 75% of our freshwater runoff. We have a water management problem, not a water shortage, but the current technology and economics cannot provide adequate solutions that strongly consider the development, management, and distribution of our abundant surface water resources.
Expansion of irrigation in the Southeast in the last 25 years has largely occurred without strong research and extension efforts in the affected states. This view is supported by the fact that roughly three quarters of the ARS irrigation research scientists are located in the western states. Currently, very few ARS water management research scientists are located in the region.
A.The need as indicated by stakeholders.
The need for research and extension is critical to develop adequate water management plans that maintain productive capacity. First, there is limited knowledge of the variations in crop water use and irrigation needs among the major crops and dominant soils in humid climatic zones. Secondly, the effectiveness and suitability of various water management strategies and scheduling tools and techniques in different crops and soils needs to be determined and improved. Studies on comparison of traditional and modern irrigation systems and their potential water and energy savings are equally scarce. The third issue is more philosophical on the surface, but has profound on-farm implications. It suggests a serious lag in awareness and adoption of the best irrigation water and system management practices in humid areas either due to historical practices, labor availability, or new irrigation in areas that were not irrigated in the past. Many producers in humid areas were raised in a rain fed culture and may not fully understand the basics of irrigation water and system management. This limits their ability to take full advantage of irrigation and its higher input requirements for achieving more stable profits and high water and energy use efficiency. Additionally, there is a need for a more critical assessment of the economics of irrigation alternatives in humid regions because rainfall can help in meeting most crop water needs in many years. Thus, the costs of installation and operation of irrigation systems over the long term must equal the benefits. In addition, small issues that have larger economic, reliability, and trust impacts (like loss of equipment, wiring, batteries; maintenance schedules under intermittent use; etc.) must also be fully addressed because farmers have neither the patience nor flexibility to sustain losses under current agricultural economic conditions. Most past efforts have addressed key knowledge gaps identified in the first two issues mentioned above, yet socio-economic and other barriers to adoption are less emphasized. These latter needs must be tackled through state-wide outreach programs that promote water-wise practices and cost-share incentives as well as help strengthening the managerial capabilities of the irrigators and the level of extension expertise in managing modern irrigation systems for high water and energy productivity. A study completed in 2006 revealed the following general technology areas and research questions needing attention across the southeast. All of these questions or technology areas have cross topic concerns.
Irrigation Efficiency
Given that there is extensive recycling of water from drainage canals and bayous onto farms, at what field-level efficiency should the farmer be operating?
Will improvements in field- or farm-level efficiency lead to large improvements in project level efficiency or is project-level efficiency already >90%?
To what extent will improvements in field- or farm-level efficiency lead to
o Improved project-level efficiencies?
o Improved economics and cost of energy reductions?
o Lower concentrations of sediment, nutrients, and pesticides/herbicides in streams?
o Improved farm economics due to more efficient use of applied chemicals and reduced irrigation pumping cost?
How much of current irrigation water demand could be met by on-farm conservation including the use of tail water pits, storage reservoirs, and replacement of earthen ditches with piping?
Irrigation application efficiencies what are they and what can they be?
What inexpensive equipment can be developed/adapted for automation and remote control of irrigation pumps?
What are the effects of irrigation storage reservoirs and tail water systems on overall farm level irrigation efficiency and water quality?
Irrigation Methods/Management
What changes can be made to make rice irrigation more efficient? Is it likely that rice irrigation methods will change away from continuous flood to more efficient methods?
What is the role of multiple-outlet paddy flooding systems?
Will other practices such as center pivot sprinklers, level basins, poly-pipe for in-field distribution to furrows or paddies, etc. increase efficiencies and economics?
Irrigation scheduling. What is the best way to schedule irrigation when water logging is as likely and harmful as water deficits? The last date to irrigate must be known to maximize soil water storage so as to reduce runoff and nutrient loss in case of rainfall after irrigation. Crop water use values must be determined for varieties and climate of the region.
What are the management guidelines for reservoir - tail water pit systems that will minimize pumping costs and maximize water capture?
What are the threshold soil water depletion levels (i.e., irrigation set points) for stress-free growth as a function of stage of growth? What is the temporal variation in effective root zone under row crops and under drip irrigated vegetables?
How does the new automated, sensor-based irrigation and fertigation scheduling compare with the current growers' practices? What is the profitability and adoption rate of automated, sensor-based irrigation and fertigation for vegetable production in the southeastern U.S.?
User friendly GIS database management for irrigation system operation would be useful.
Commercial systems exist for center pivot systems. Can a similar system be developed for surface irrigation systems that include reservoirs, tail water pits and re-lift pumps?
Social Issues
How will competing interests of agricultural, industrial, and municipal users be resolved?
What are the competing entities and their water requirements now and in the future?
What is the federal government's interest in water resource development, and what should the goals be?
Socio-economic studies are needed. A study has been done for Grand Prairie but not elsewhere.
Arkansas generates approximately 80 million acre-feet of runoff yearly. There is a need to develop 10% of this. How should it be done?
As irrigated acreage decreases in the semi-arid Great Plains and arid west, what pressures will occur to change irrigation (crops, efficiencies, methods) in the LMRV and southeast United States?
Soil - Irrigation Interactions
What are pertinent soil properties that will influence possibilities, opportunities and outcomes for irrigated agriculture?
Some soils in the Lower Mississippi River Valley (LMRV) appear to be hydrophobic. How can they be ameliorated?
Hydraulic conductivities are low in typical soils of the LMRV, which are extremely low in organic matter and have massive structure. Which irrigation methods are favored in these soils?
What are organic matter effects on soil physical characteristics?
Fragipans and tillage pans are common in LMRV soils. How do they affect irrigation efficiencies and yields and what remediative measures are appropriate?
Irrigation Project Design and Management
How is the hydrology and water balance of irrigated areas affected by design alternatives such as on-farm storage reservoirs, tail water pits, and re-lift pumps?
What is the life of storage reservoirs being built today?
What can be done to control embankment erosion, which is a serious problem in the uncohesive silt loam soils common in the region? Are there chemical soil treatments such as poly acrylamide (PAM) that can control erosion? Are there more effective and cost-effective seeding options?
What is the life of tail water pits being built today? What is the rate of sedimentation in tail water pits?
Production Practices/Agronomics
What are the effects of row spacing and plant density on irrigation efficiency and the economics of production?
What are the effects of PAM on soil erosion and infiltration in irrigated systems?
Crop water use measurement and prediction. To what extent can irrigation scheduling improve water and nutrient management in a system where water is captured in tail water pits and recycled?
No-till rice production to improve soil organic matter and thus structure and related properties.
How do tillage practices affect crop water use?
How do hydroponics and sprinklers fit into the water re-use practiced on SE Arkansas farms that produce fish, rice, and cotton simultaneously?
B. The importance and extent of the problem.
There is strong debate in Arkansas on the wisdom of diverting surface water from rivers for irrigation. This same debate is occurring in Florida, Alabama, and Georgia as a result of the water wars in that region, and the implementation of new approaches to manage water within geographic and political boundaries. This debate will not be limited to these locations alone, and will escalate as agricultural water use competes with other consumptive needs (municipal, industrial, etc.), societal needs and environmental considerations. The debate centers around effects of diversion or use on important sport fisheries, on riparian wildlife and habitat, on maintenance of adequate stream flows during the summer months, and on water quality. These conflicting needs generate a demand that water diverted for irrigation is used as efficiently as possible, and that environmental impacts are minimized for well designed and operated irrigation schemes. Irrigation water use efficiency at field, farm, and project levels, irrigation project design alternatives to improve overall water use efficiency, and enhanced knowledge transfer to producers are research topics that are of critical importance to the successful management of our water resources. It is also critically important as water allocations are considered from existing streams, lakes, and reservoirs.
C. The technical feasibility of the research
Each participant in this research program has experience with irrigation research and/or is associated with a funded (or anticipated) irrigation research park or facility. Project plans and procedures indicated below outline the scientific basis for high quality research that is publishable in refereed journals as a basis for clientele decisions.
The organizational support for irrigation research is quite extensive throughout the humid and sub-humid region indicating this type research is a priority. The potential to meet irrigation research needs while minimizing duplication across similar crop, climatic, and physiographic locations encourages more efficient utilization of funding for irrigation research. For example, irrigation research on scheduling of peanut irrigation occurs in Georgia (more than one location), Florida, Alabama, and Texas. Researchers are investigating computer-based irrigation scheduling to sensor feed-back controls to on-farm irrigation scheduling devices. Each of these approaches has merit to a different population of farmers and other end users involved in irrigation. However, collaborations across locations are expected to yield more comprehensive results.
D. The advantages of doing the work as a multi-state effort.
Local efforts are underway to address certain issues but are generally not set up as research trials. S1018 encourages the exchange of information and serves as a mechanism to facilitate information and technology exchange. Information such as projects, project objectives, studies, available reports, technology utilized, and general results are being exchanged. Before the S1018 project, there was no formalized process to exchange basic information among agencies and with organizations outside of the multi-state project approach. The first five-year humid area irrigation project, S1018, started the process, but there is still much that needs to be done. The multi-state project following S1018 will continue to serve as the forum to exchange information on projects and studies that address surface water, runoff, water quality, and similar water related issues tied to agricultural irrigation across humid areas.
E. Benefits or impacts of the research or information exchange including impact on science.
Using a multi-state approach to meet these objectives will allow plot, field and national-scale methodologies to be implemented with a reduced potential for overlap between locations. In addition, technologies can be explored for compatibility across different physiographic, soil, and climatic conditions to ensure application potential of resulting technologies. For example, cotton is irrigated in several locations throughout the humid region. Irrigation scheduling, profitability characteristics as associated with irrigation water management, and cultivar responses to irrigation management alternatives would benefit from a comprehensive regional effort.
Landscape and turf irrigation are also practiced across the entire humid and sub-humid region. The potential to save water via conservation based upon improved sensor technology and better scheduling could reduce the potential for implementation of severe water restrictions. Within the past ten years, severe restrictions to complete outside watering bans have been utilized in many communities in humid and sub-humid areas to help conserve water resources. Individual users and the nursery industry (one of the fastest growing agricultural enterprises in the United States) would greatly benefit from proactive water management approaches that could ward off or mitigate watering restrictions.
Irrigation water management strategies have primarily been developed in areas where rainfall is minimal. The application of water management strategies developed for arid conditions to the humid and sub-humid region may have significant limitations, especially with regard to irrigation scheduling. Irrigation research will require a more critical assessment of economic potential and risk assessment based upon rainfall probabilities in humid and sub-humid areas. The long-term benefits must exceed the costs to install and operate irrigation systems before the technology will be adopted on a large scale in agriculture.
F. Identify the stakeholders, customers, and or consumers of the project results.
The most important benefits from this research will be the community of people living and working in humid areas. Irrigated farms throughout the humid and sub-humid region, homeowners and businesses with irrigation, state and national agencies that are responsible for reducing water consumption and improving water management, and all those who benefit from another water user improving their water use efficiency will benefit from this research and technology transfer effort. Irrigation and water applications are a component in a comprehensive analysis of costs and returns on those investments. In Florida, for example, the stakeholder group includes at least 15 million water users and consumers. An in-ground irrigation system is standard in new home construction in the state, and Florida has a significant proportion of all new home construction in the US. In North Carolina, there are multiple pending bills that address water use across multiple sectors and that seek to allocate water based upon consumptive use. Increasingly, states in humid areas have to implement water management strategies to address increasingly limited water resources and competition between urban and agricultural users.
Specific stakeholders include but are not limited to: Members of South Carolina Cotton Board and South Carolina Soybean Board, Cotton Incorporated, SC Department of Environmental and Health Control (DHEQ), North Carolina Division of Water Resources, the vegetable industry (as represented in numerous meetings, i.e., South Carolina / North Carolina Vegetable Expo, Southeastern Vegetable Expo, Eastern Shore Ag. Expo, SC Specialty Crops annual meeting), Alabama Cotton Commission, AR Rice Research Promotion Board, Yazoo Water Management District, National Water Management Center.
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