MODELING WATER UTILIZATION IN LARGE-SCALE IRRIGATION SYSTEMS: A QUALITATiVE RESPONSE APPROACH1

ABSTRACT: Given limited available data and the present state of knowledge on the social aspects of irrigation, there is a need to develop new quantitative methods to measure water management performance in large-scale systems. A qualitative response framework is adapted to formulate a dynamic logit model of weekly field water adequacy and quantify indirectly farmer water utilization. Model parameters are estimated in a weighted least-squares regression using four seasons of data from a Philippine canal system. Estimated coefficients and independent model forecasts indicate greater effective use of rainfall than irrigation in sustaining high levels of water adequacy during the rainy season. Irrigation utilization is two times higher in the dry season, while system location has a much smaller but still significant impact. Utilization rates for both rain and irrigation showed considerable responsiveness to the prevailing scarcity of water. The qualitative response approach is well suited to the aggregated data available for large-scale systems, and allows advances in modeling dynamic water management behavior. Formal evaluation of the model will require further empirical applications.     

SUPPLEMENTAL IRRIGATION OF HORTICULTURAL CROPS IN THE HUMID REGION1

ABSTRACT: A computer model was developed in order to establish a yield predictive relationship and to estimate the water requirements for supplemental irrigation of horticultural crops in the humid region. Alternative distribution systems were developed and designed using the results from the computer model and Wood's (1980) pipe network algorithm. The capital, operational, and maintenance costs of the distribution and recommended on-farm irrigation systems were determined and used to evaluate the economic feasibility of the alternative designs. Results show that the concentration of irrigated area along the distribution system, the length of the distribution system, and cropping system all have an important effect on the economic feasibility of supplemental irrigation in Wayne County, Kentucky.     

AN INDEX FOR MEASURING THE PERFORMANCE OF IRRIGATION MANAGEMENT SYSTEMS WITH AN APPLICATION1

ABSTRACT: This paper presents a statistically valid index for measuring the performance of irrigation systems. The index is applied to a sample of 39 farms on a watercourse under the warabandi system of irrigation management in India. It is found that while the farmers in fact irrigated almost exactly the total amount of irrigated area as designed, inter-farm variations were considerable. The index shows that the degree of error of managerial effectiveness of irrigation on this watercourse is 20 percent. Therefore it is concluded that the system is performing at 80 percent effectiveness.     

A STUDY OF WASTEWATER IRRIGATION THROUGH COMPUTER SIMULATION1

Wastewater irrigation is a re-emerging method for dealing with an area's wastewater, particularly in Northern temperate climates in the U.S. Muskegon, Michigan, typical of a medium-sized Northern urban area, is currently adopting wastewater irrigation to meet its present and future wastewater treatment needs.     

TRENDS IN WESTERN UNITED STATES AGRICULTURE: IRRIGATION ORGANIZATIONS1

ABSTRACT: From 1940 to 1978, irrigated acreage in the Western United States increased by over 150 percent, irrigated acres per farm increased by 204 percent, and the number of irrigation organizations grew by 31 percent. Understanding the factors affecting these trends (in the structure of irrigated agriculture) is the key to formulating policies for efficient allocation and transfer of water in the west. Four variables that impact the composition of irrigation organizations are farm size changes, organizational efficiency, intersectoral competition for water, and governmental policies. The conclusions show that from 1940 to 1978, the total number of irrigated farms and organizations declined, and the average farm size increased, and larger management oriented organizations such as districts and U.S. Bureau of Reclamation have become more prevalent. With respect to total quantities of water delivered, districts have increased over 50 percent since the 1959 Census and over 100 percent since the 1950 Census, while unincorporated mutuals have declined by approximately 20 percent. Future organizational structure tends to be moving in the direction of more management control as opposed to user control. Changes in water use, delivery, investment, transfers, and laws will continue to change the structure of irrigation organizations and institutions in the west.     

PATTERNS AND TRENDS IN IRRIGATION EFFICIENCY1

ABSTRACT: Irrigated agriculture is one of the most important water-use sectors in terms of total water diversion and consumptive use. For at least the last 25 years, improving irrigation efficiency has been a widely advocated and accepted goal. This paper uses a sample of 16 Bureau of Reclamation irrigation projects to examine the pattern of average irrigation efficiency and change in efficiency over time. In general, the highest average efficiencies are found in the arid Southwest while the lowest are found in the semi-arid to sub-humid Great Plains region. Over the 22-year period of analysis, there has been no observable trend toward improvement in efficiency at any of the projects.     

A LOW COST DRIP IRRIGATION SYSTEM FOR SMALL FARMERS IN DEVELOPING COUNTRIES1

ABSTRACT: In areas where water is scarce, drip irrigation provides the most efficient way to conserve irrigation water, but its cost of £1000 an acre is prohibitive for most small farmers in developing countries. The cost was reduced by 90 percent by (1) making dripper lines moveable, so that each line reaches ten rows instead of one; (2) replacing 25-cent emitters with simple 0.70 mm holes punched by a heated needle; and (3) using £3.00 off-the-shelf 20 liter containers with cloth filters in place of expensive filter systems. This reduced the cost of a half-acre system to £50. The low cost system was field tested in the hill areas of Nepal, and in mulberry cultivation in Andhra Pradesh, India. Uniformity of flow from emitters was 73–84 percent. Small farmers reported that the low cost trickle irrigation system cut labor requirements in half, and doubled the area irrigated by the same amount of water. The low cost drip system is likely to be widely adopted by small farmers in semi-arid and hilly regions.     

IMPROVING IRRIGATION WATER MANAGEMENT IN THE INDUS BASIN1

ABSTRACT: Over half of the water delivered from the canal system to the watercourses managed by the farmers is not made available to the farmers' crops in Pakistan. Most of this water loss is due to loss of water through the banks of the watercourses. Lack of maintaining these banks and lack of cleaning the watercourse is a result of inadequate organization of the 10 to 150 farmers who use the watercourse, and a deficiency of knowledge concerning the amount of their water which is being lost. Various methods of watercourse improvement have been evaluated including concrete and masonry linings and simple earthen improvements of the ditches with concrete control structures, junctions, and turnouts. With the cost of labor low in Pakistan, the earthen improvements with concrete structures appear to be the best investment. Farm water management improvement programs have been implemented in most of the provinces which include this type of watercourse improvement, land leveling and advice to the farmers on how and when to irrigate his crops to optimize his production. The rate at which personnel can be trained to help the farmers implement these improved water management practices is limiting the rate of implementation.     

ESTIMATING IRRIGATION WATER USE THROUGH SELECTIVE MONITORING: A NORTH FLORIDA CASE STUDY1

ABSTRACT: Selective placement - under a rigorous statistical sampling design - of newly available monitoring equipment on irrigation systems may provide effective and economical estimates of total irrigation water use in areas where complete water use inventories are impractical. In 1979, a joint effort by the U.S. Geological Survey and Florida's Suwannee River Water Management District was launched to estimate the District's 1979 irrigation water use using a selective monitoring approach. Analysis of previous inventories of irrigation equipment and amounts of water applied in the District indicated that total 1979 water use estimates with six to nine percent sampling error could be obtained using selective monitoring, given the time and equipment limitations for the monitoring program. Restricting monitoring to a sample of farms can introduce systematic error to water use estimates if farmers' participation is related to their water use methods. Preliminary results of the 1979 study indicate tht declining participation rates, if unchecked, could lead to serious systematic eror in future North Florida selective monitoring studies.     

ASSESSING INSTREAM FLOWS AND RESERVOIR OPERATIONS ON AN EASTERN IDAHO RWER1

ABSTRACT: A methodology for assessing reservoir management was applied to the historical conflict between winter fish and wildilife flows below Island Park Reservoir on Henrys Fork of the Snake River and the fulfillment of storage water rights. The methodology consists of (1) identifying impacts of flow regulation, (2) quantifying relationships among variables affecting physical reservoir fill, and (3) assessing effects of these discharges on the fulfillment of water rights in the context of a larger system of interrelated reservoirs. Winter (storage season) flows are critical to management of fish and wildlife populations below Island Park Dam, but flow regulation has resulted in decreased winter discharge. Allowable winter flows are a function of inflow, length of storage season, reservoir content at the start of storage season, and potential for downstream capture of excess storage season water discharged at Island Park. Modeling results indicate that winter flows in the range of those recommended for fish and wildlife management are attainable during average years but not during years when initial reservoir content is low. The methodology was successful in quantifying information useful to decision makers in a variety of agencies and disciplines and could be applied to solve water management problems on other regulated river systems.     

MODELING FLOW IN THE EVERGLADES AGRICULTURAL AREA IRRIGATION/DRAINAGE CANAL NETWORK1

ABSTRACT: The south Florida ecosystem and Lake Okeechobee are important water resource areas that have degraded due to changes in hydroperiod, water supply, and water quality. Approximately 56 percent of the total phosphorus in water discharged from the Everglades Agricultural Area (EAA) is in particulate form. Currently, farm-level best management practices are being implemented in the effort to reduce total phosphorus and sediment in off-farm discharges. The objective of this work was to develop and calibrate a model describing water movement in primary EAA canals as a first step to development of a water quality (i.e., nutrient, sediment) model. The Netherlands-developed mechanistic flow and water quality model (DUFLOW) was adapted for the EAA. Flow, stage, geometry, canal network, and meteorological data, October 13, 1993, to February 13, 1994, were used to adapt and calibrate the DUFLOW model for EAA water level and flow in primary canals. Direct runoff discharge into the primary canals from farm-pump stations was used as runoff input for the model. The model results are comparable to an independently-calculated water balance for the EAA. The calibrated flow model will be the basis for the calibration of sediment and chemical transport in the future.     

OPTIMIZATION OF WATER RESOURCES FOR IRRIGATION IN EAST JORDAN1

The paper describes an approach towards optimal allocation of surface and ground water resources to three agricultural areas in the Jordan Valley under conditions of scarce water supply. The optimizing model allocates water from three main rivers, each with reservoir storage, and from two ground water sources to three irrigation regions. Productivity of irrigation water, expressed as the net present value of the regional agricultural output, but allowing for crop water deficits, is first maximized using nonlinear programming. The allocation process then adopts techniques of linear programming to determine the least cost alternative based on the unit cost of water from each resource at each destination, as it varies with time.     

ESTIMATING THE DEMAND FOR IRRIGATION WATER IN THE CENTRAL VALLEY OF CALIFORNIA1

ABSTRACT: This paper computes estimates of the demand for surface irrigation water directly from disaggregated profit functions for fields in the San Joaquin Valley of California. It finds that treating delivered surface water and pumped ground water as separate, imperfectly substitutable inputs to production matters a great deal. We find substantial ranges of inelastic demand for delivered water, and thresholds across which demand then becomes highly elastic. The results imply that moves toward freer water markets could lead to large quantities reallocated from agriculture to urban uses in the Western U.S., but would require large price increases and would induce extensive ground water mining and major changes in cropping patterns. While these results are dependent on our particular model and simplifying assumptions, evidence exists that they may be robust.     

A RAWLSIAN EVALUATION OF IRRIGATION DISTRIBUTION IN INDIA1

ABSTRACT: This paper critically evaluates the nature of irrigation distribution in India using the Rawlsian criterion of equity in dis. tribution and estimates the performance of different states in India according to the Rawlsian notion of fairness in distribution. It is found that there is considerable inequality across farm-size groups in the distribution of irrigated areas in general and canal irrigated areas in particular, and that there are wide interstate differences in the levels of this inequality. Further, it is found that switching over to a Rawlsian based distribution of canal irrigation will help in reducing the levels of inequality in overall irrigation distribution in all states.     

VALUING IRRIGATION WATER: A SIMULATION/MATHEMATICAL PROGRAMMING APPROACH1

ABSTRACT: A two-stage simulation/mathematical programming model was developed to derive irrigation water values that reflect efficient response to reduced water supplies. The failure of many previous water valuation studies to represent the dynamic dimension of irrigation was shown to result in overestimation of derived water values. Water values are also shown to be dramatically influenced by both application system characteristics, as well as the relative costs of irrigation inputs. Finally, the marginal value of irrigation water was shown to vary considerably over the irrigation season, reaching its maximum when atmospheric demand is highest and crops are most susceptible to water stress. Results presented should be of interest to policymakers investigating the viability of alternative water reallocation mechanisms.     

PRIVATIZING GOVERNMENT IRRIGATION PROJECTS IN NEW ZEALAND1

ABSTRACT: This paper discusses the sale of the Government. owned irrigation projects in New Zealand, including the development of irrigation projects in New Zealand, the rationale behind the transfer of ownership to existing irrigators, the sale process, and the outcomes. The transfer of ownership to private entities was undertaken primarily to remove the Government from irrigation activities. However, the sales were also thought to have the poten. tial to improve the efficiency of the projects' operation. The sale process was a negotiated process so that maximizing revenues was not the primary objective of the government. In many cases the government paid irrigators to assume ownership of the schemes. Preliminary data suggest that schemes are being more efficiently operated under private ownership. However, additional data need to be collected on a systematic basis to determine the magnitude of any efficiency gains.     

AN EVALUATION OF THE 1997 EDWARDS AQUIFER IRRIGATION SUSPENSION1

ABSTRACT: In early 1997, the Texas Edwards Aquifer Authority implemented a pilot Irrigation Suspension Program with the objectives of increasing springflow and providing relief to municipalities during drought. Irrigators were paid an average of $234 per acre to suspend water use, a price higher than regional land rental rates. Auction theory and program implementation details suggest that the program implementation partially caused inflated bids. The Irrigation Suspension Program is also compared to two alternative programs: (1) subsidizing more efficient irrigation technology and (2) buying land. The irrigation suspension is found to be more cost‐effective relative to subsidizing improved irrigation efficiency because it can be put in place only when aquifer levels are low. Land purchase is a cheaper alternative if the bid levels remain at the levels observed.     

PRICING IRRIGATION WATER IN DEVELOPING COUNTRIES1

ABSTRACT Alternative combinations of water pricing and regulations are possible in allocating irrigation water. The best combination will depend on the value of water, ability to control deliveries, desire to subsidize agriculture, ownership traditions, crops grown, return flows, drainage problems, staff training, ability to collect fees, the number of farmers involved, etc. Marginal cost pricing is just one possible alternative and it is more a way of thinking about prices rather than a set system. The possibilities for achieving an equitable and efficient distribution of water are improved if some form of marginal cost pricing is included in the system of water charges.     

CLIMATE CHANGE,IRRIGATION, AND CROP RESPONSE1

ABSTRACT: A set of simulation models consisting of a weather generator, and irrigation supply, soil moisture and crop growth components was used to evaluate the impacts of climate change on irrigated corn in locations near Albany, New York, Indianapolis, Indiana, and Oklahoma City, Oklahoma. The models evaluated the combined effects of modified water demand, supply and crop management (planting date, cultivar selection, irrigation). Simulations were duplicated for 100-year weather sequences based on current (1961–1988) weather statistics, and statistics modified by outputs from the GFDL GCM runs showing the effects from doubling of atmospheric CO₂. Climate impacts differed greatly with location and management. Effects were most adverse in New York and least damaging in Indiana. At all sites, the beneficial effects of longer growing season and increased water supply were generally overcome by the detrimental impacts of increased evapotranspiration and reduced solar radiation during plant maturing stages. Adverse impacts of climate change can be substantially reduced by irrigation and appropriate selection of planting dates and cultivars.     

IRRIGATION PLANNING BASED ON WATER DEFICITS1

ABSTRACT: The deliberate underwatering of a larger land area, as practiced in Southern Asia, has provided impetus for a systematic investigation into the effects of designing projects for crop water deficits on Benefit-Cost performance. The study began with the derivation, from published experimental results, of functions relating ultimate crop yield to the magnitude and timing of water deficits, i.e., of the productivity of irrigation water. To obtain the net benefit of the project, the relation between the harvested area and output and the on-farm production costs was then suggested. The cost of supplying the irrigation water to the proposed area and of distributing and applying it to the field was determined, thus completing the Benefit-Cost equation. A computer simulation model was then established to search for the irrigation project design capacity and area to maximize the net present value in the Benefit-Cost analysis for the development proposed.