Evaluation of irrigation water measurement methods and devices in South Africa

摘要

A three year long research project, funded by the Water Research Commission of South Africa,rncommenced in 2001 with its main objectives being to assess the current status of irrigation waterrnmeasurement in South Africa and to establish guidelines for the correct choice and management ofrnflow measurement devices for irrigation water from different distribution systems (canals, pipelinesrnand rivers).rnAn assessment of the current situation identified one of the biggest problems in practice to be thernmeasurement of water abstracted from rivers by individual farmers using motor-driven pumps. Thernremoteness of the sites, the quality of the water, the complications of pumps being privately owned,rnand the general resistance of the farmers to having the water measured have in very few cases beenrnovercome by the WUAs in their search for affordable, reliable and tamper-proof measuring devices.rnAs a result, two methods of indirect measurement for estimating water use are being investigated,rnfirstly measuring and recording the pressure on the up-stream and downstream sides of the pumprnand relating it to the actual discharge through calibration, and secondly, measuring and recordingrnthe power consumption of the pump and relating it to the actual discharge through calibration.rnThe paper addresses the results of these evaluations and how they contribute to the formulation ofrnguidelines for WUAs on issues such as required accuracy of measurement methods and devices,rnautomation of measurement systems, performance of devices compared to conventional meters asrnwell as cost-effectiveness of new approaches.