An Instrumented Lysimeter System for Monitoring Salt and Water Movement

A lysimeter system is described which consists of four continuously weighing lysimeters mounted on a portable platform. The lysimeters, made from low pressure PVC irrigation pipe (1.18 m deep by 0.31 m dia), are placed on a hydraulic weighing system that consists of either a water-filled rubber pillow or an automotive innertube connected to a water column. The sensitivity of the weighing system is 0.1 kg or an equivalent water depth of 1.4 mm. One bar ceramic cups, placed in the center of the lysimeters at 0.25, 0.50 and 0.75 m from the soil surface, are connected to the outside for soil solution sampling. Eight small bolts symmetrically located around the lysimeter at the same depths as the ceramic cups, serve as "four probe" contacts for electrical conductivity measurements. The cost of each set of four lysimeters in 1978 was about $400

Recirculating Farm Irrigation Systems

A survey of systems for recirculating runoff water from irrigation in southern Idaho shows little evidence of formal system design. Systems were constructed to handle approximately 20 percent of the volume of irrigation water. Costs of the systems vary with the type of installation. Sequence, reservoir, and cycling sump systems each has certain advantages. Recirculating systems are not effective unless the water is applied to a different area than that which is contributing runoff. Recirculating irrigation systems can raise water application efficiencies to 80 percent

Recirculating Farm Irrigation Systems

A survey of systems for recirculating runoff water from irrigation in southern Idaho shows little evidence of formal system design. Systems were constructed to handle approximately 20 percent of the volume of irrigation water. Costs of the systems vary with the type of installation. Sequence, reservoir, and cycling sump systems each has certain advantages. Recirculating systems are not effective unless the water is applied to a different area than that which is contributing runoff. Recirculating irrigation systems can raise water application efficiencies to 80 percent

Reuse of drainage water from irrigated areas

Increasing competition for water of good quality and the expectation that at least half of the required increase in food production in the near-future decades must come from the world's irrigated land requires to produce more food by converting more of the diverted water into food. Reuse of the non-consumed fraction ('drainage water') of the irrigation water already diverted is a proven but risky option for better fresh water management. This paper presents an overview of different options for reuse of drainage water and guidelines for its safe use. Criteria for maximum irrigation water salinity to prevent soil deterioration and crop yield reduction, for the maximum concentration of toxic substances and limits for bacteriological water quality are given. Examples of sustainable reuse of drainage water in Egypt, India and the USA are presented. The usefullness of simulation models for the analysis of regional water and salt balances is demonstrated

Analysis of effective efficiency in decision making for irrigation interventions

Multiple stresses are putting great pressure on water resources systems. Population growth, cli mate change, prosperity, energy production, food crisis, and water governance are among the factors straining water resources. Decision makers from rich to poor countries and from commercial to non governmental organisations are struggling to devise schemes to adapt to these stressed water conditions. Better efficiency for water resources systems, and particularly irrigation systems, is recommended as one of the most important responses to climate change, unsustainable development, and water shortage. However, using certain effi ciencies such as Classical Efficiency caused systems not to perform according to decision makers' objectives. Effective Efficiency is a robust composite indicator that includes in its formulation both a flow weight, taking into account the leaching fraction, and reuse of return flows. Classical Efficiency is defined as the percentage of the diversion consumed beneficially, such as by crop evapotranspiration. Effective Efficiency, on the other hand, is defined as the ratio of beneficial consumptive use to total consumption, expressed as a percentage. In this paper, a normalised and non dimensional form of Effective Efficiency is developed and necessary con straints for its successful application are explained. These constraints express water balance, flow weights and their thresholds, water reuse, and total consumptive use. Basic guidelines are proposed for better decision making in determining possible interventions for improving Effective Efficiency. This is done by analysing its domain through analytical and graphical methods. Three real cases are considered, namely, Imperial Irriga tion District and Grand Valley irrigation systems in the United States and Nile Valley in upper Egypt. Three dimensional sensitivity analysis is performed on Effective Efficiency and its variables using the three cases. This leads to an examination of the validity of the analysis and to suggestions for better intervention options. Meanwhile, it is also shown why Classical Efficiency should be used with care.Fundação para a Ciência e a Tecnologia (FCT