Ramchand Oad

Comparison of Laboratory and Field Calibration of a Soil-Moisture Capacitance Probe for Various Soils

AbstractThroughout the American west, irrigated agriculture has been targeted to increase water-use efficiency because of increased urban demands. Soil-moisture sensors offer a method to achieve efficiency improvements, but have found limited use primarily because of high cost and lack of soil-specific calibration equations. In this paper, the Decagon EC-20 soil-moisture sensor (a low-cost capacitance sensor) has been examined and a unique laboratory-calibration method has been developed. Field-and laboratory-calibration equations were developed for six soil types (sand, sandy loam, silt loam, loam, clay loam, and clay) in the Middle Rio Grande Valley for alfalfa and grass hay fields. The average absolute error in volumetric water content for field calibration was 0.430  m3/m3, and 0.012  m3/m3 for the laboratory calibration. The factory-calibration equation for the EC-20 was also evaluated and found to yield an average absolute error of 0.049  m3/m3. In this study, it was found that the EC-20 is a reliab...

Variable-time model for equitable irrigation water distribution

Abstract The existing warabandi system used in Northwest India and Pakistan is analyzed and the effect of conveyance losses on the water distribution has been studied. It is shown that water distribution within a watercourses command under the existing warabandi system is not equitable. The watercourses are earth channels that lose water due to seepage. Since the existing warabandi allocates equal time per unit area, the landholdings situated at the end of the watercourse receive less water than those near the watercourse outlet. A variable-time model is proposed for irrigation water distribution within the watercourse commands. The model achieves equity of water distribution by increasing the irrigation time per unit area for the downstream landholdings on a watercourse. The increase in irrigation time is determined in proportion to the seepage loss rate. Two case studies of watercourse commands in India and Pakistan confirm the validity of the variable-time water distribution model.

Decision support systems for efficient irrigated agriculture

Water is the lifeblood of the American West and the foundation of its economy, but it remains its scarcest resource. The explosive population growth in western urban areas, the emerging need for water for environmental and recreational uses, and the national importance of the domestic food production from western farms are driving major conflicts between these competing water uses (US Department of Interior, 2003). Irrigated agriculture in particular is by far the largest water user – 80% countrywide and 90% in the Western U.S – and since it is perceived to be a comparatively inefficient user, it is frequently asked to decrease its water consumption. Irrigated agriculture in the Middle Rio Grande diverts large quantities of river water, which is believed to leave insufficient water to meet other societal needs such as urban and wildlife requirements. This paper will present our research on options to make irrigation system operations more efficient. Most irrigation systems can meet their users’ needs with decreased river diversions by adopting operational procedures, which are based on real-time knowledge of available water supplies and crop water requirements. The paper will describe our on-going research in the Middle Rio Grande Valley, to develop a Decision-Support System (DSS) that can assist water managers to closely match water deliveries to crop water requirements, thereby reducing river diversions. The DSS uses linear programming logic with an objective function to find an optimum water delivery schedule for the service areas in an irrigation system. Water delivery using the DSS is accomplished using three modules: a water demand module, a supply network module and an irrigation scheduling module. Limited field validation shows that the DSS is indeed able to correctly model the irrigation delivery system, and recommend water delivery schedules that are reasonable. Future plans include more intensive field validation and implementation in the Middle Rio Grande irrigation service area.

Performance measure for improving irrigation management

A measure to evaluate performance in irrigation systems is analyzed using the mean square prediction error concept. In the context of irrigation system management, the term error means the deviation of actual performance from a reference performance. The measure assesses performance in terms of the management objectives of adequacy and dependability of water delivery and an equitable distribution among various water users. It provides an understanding of the management capacity to schedule and distribute water in an irrigation system. Application of the performance measure is demonstrated by evaluating performance of an irrigation system in the Northwest Frontier Province of Pakistan.

Irrigation Policy Reforms for Rice Cultivation in Egypt

This paper reports a fieldresearch that evaluated irrigation waterdelivery options for promoting conservativewater use in rice cultivation. Ricecultivation in the Delta region of Egypthas grown dramatically, replacing cotton asthe major summer crop. The Ministry ofWater Resources and Irrigation is findingit difficult to limit the area planted torice since rice cultivation is profitableto farmers. A socially more feasibleoption is to encourage farmers to cultivateshort-season rice varieties. The Ministrycan then adopt the policy that will provideirrigation water to the farmers to supportcultivation of 120-day rice varietiesrather than 160-day traditional varieties. The field studies conducted for two yearsin the Nile Delta conclusively show thatthis is indeed feasible. Farmers in thedemonstration canal areas were able tosuccessfully finish 120-day ricecultivation, which allowed the Ministrystaff to end the rice water delivery about35 days early and realize substantial watersavings.

Validation of a Decision Support System for Improving Irrigation System Performance

AbstractTo address water shortage and improve water delivery operations, decision support systems (DSSs) have been developed and utilized throughout the United States and the world. One critical aspect that is often neglected during the development and implementation of DSSs is validation, which can result in flawed water distribution and rejection of the DSS by water users and managers. This paper presents the results of a significant validation effort for a DSS in the Middle Rio Grande Conservancy District (MRGCD). The validation resulted in a refined application efficiency of 45%, a refined readily available water for farmers to irrigate to a value of 20%, and a Nash-Sutcliffe modeling efficiency of 0.86 for soil moisture depletion patterns. Overall, the validation and refinement of input parameters resulted in a DSS model that accurately predicts evaportranspiration and can be used to schedule water delivery. The refinement of the DSS input parameters resulted in an increased 15,600 acre-ft diversion ...

Modelling water control needs for diversified cropping.

The background and concepts of water control for crop diversification in rice-based irrigation systems are discussed. Water control is described in terms of the irrigation event volumes and intervals between irrigation events. The development of the WACCROD model to simulate these water control parameters under selected agroclimatic conditions is described. The simulation model can recommend irrigation event volumes and intervals for various dry season cropping patterns in rice-based irrigation systems. Also, the application of the model to a general situation at field level of a ‘typical’ rice based irrigation system is reported.

Implementation of a Decision Support System for Improving Irrigation Water Delivery: Case Study

AbstractDecision support systems (DSSs) for irrigation system management have many benefits, which include water savings and the development of optimal water delivery schedules, while maintaining farmer productivity. To address water shortage and improve water delivery, DSSs have been developed and utilized throughout the United States and the world and can be used to predict crop depletions using weather data to schedule water delivery on the basis of crop demand. The overall utility of DSSs is that they allow managers to continue water delivery and equitably distribute supplies during a water shortage. For a decision support system to be successfully utilized, the complicated challenge of implementation needs to be addressed. Decision support system implementation is often met with harsh resistance from water users and managers alike, and, in many cases, a scientifically sound model is often rejected because of misinformation and lack of user education. This paper presents the successful implementation ...

Linking a Developed Decision Support System with Advanced Methodologies for Optimized Agricultural Water Delivery

Water is the lifeblood of the American West and the foundation of its economy, but it remains its scarcest resource. The explosive population growth in the Western United States, the emerging additional need for water for environmental uses, and the national importance of the domestic food production are driving major conflicts between these competing water uses. Irrigated agriculture in particular is by far the largest water user of diverted water – 80% country wide and 90% in the Western U.S – and since it is perceived to be a comparatively inefficient user, it is frequently asked to decrease its water consumption. The case of the Middle Rio Grande illustrates the problem very well. The Rio Grande is the ecological backbone of the Chihuahuan Desert region in the western United States, and supports its dynamic and diverse ecology, including the fish and wildlife habitat. The Rio Grande Silvery Minnow is a federally listed as endangered species, and irrigated agriculture in the Middle Rio Grande has come under increasing pressure to reduce its water consumption, while maintaining the desired level of service to its water users. Irrigated agriculture in the Western United States has traditionally been the backbone of the rural economy. The climate in the American West with low annual rainfall of 10 to 14 inches is not conducive to dry land farming. Topography in the West is characterized by the Rocky Mountains which accumulate significant snowfall, and the peaks of the snowmelt hydrograph are stored in reservoirs allowing for irrigation throughout the summer crop growing season. Of the total available surface water irrigated agriculture uses roughly 80 to 90% (Oad and Kullman, 2006). The combined demands of agriculture, urban, and industrial sectors in the past have left little water for fish and wildlife. Since irrigated agriculture uses roughly 80 to 90% of surface water in the West, it is often targeted to decrease diversions. Due to wildlife concerns and demands from an ever growing urban population, the pressure for flow reductions on irrigated agriculture increases every year. In order to sustain itself and deal with external pressure for reduced river diversions irrigated agriculture has to become more efficient in its water consumption. This chapter focuses on research regarding improving water delivery operations in the Middle Rio Grande Conservancy District system through the use of a decision support system linked with advanced infrastructure, methodologies, and technology.

Irrigation water management for crop diversification: Application of the WACCROD model

The actual water management practices, in terms of the volumes and intervals of delivery, are examined in a rice-based irrigation subsystem where crop diversification is practised. A simulation model (WACCROD) is used to generate the hypothetical water requirements of the changing crop mixture at quartenary and tertiary levels.Crops other than rice were planted in the dry season to reduce the need for water. Then, as the available water supplies diminished, the volume and timing of water deliveries changed based on the time, hydraulic location and relative importance of the crop.