Accuracy of project-wide water uses from a water balance: a case study from Southern California

Abstract

A detailed water balance was conducted on the Imperial Valley in Southern California for the years 1987 to 1996. The area included all lands within the boundaries defined, including farms, towns, road, etc. This analysis included surface and subsurface inflows, rainfall, surface and subsurface outflows, evaporation, evapotranspiration, municipal and industrial uses, etc. Total water consumption was computed as the remainder in the water balance. The accuracy of this quantity was determined from standard statistical procedures based on the accuracy of the input data. For the Imperial Valley, total water consumption was estimated to within ±4.5%. The various sources of water and destinations were partitioned so that the accuracy of each component could be determined. The method also determines the source of uncertainty through the variance of each measurement. Subsystems were defined so that other quantities of interest could be determined. A canal subsystem water balance was used to determine more accurate estimates of water delivered to farms. A drainage/river subsystem water balance was used to determine the amount of irrigation return flows. Finally, the destinations of irrigation water were delineated and the Irrigation Consumptive Use Coefficient (ICUC) was calculated. The confidence interval, as a 10-year average, was 0.64<ICUC>0.70. It was shown that the uncertainty of rainfall and how that water is partition has a significant influence on the accuracy of the estimated water consumption and ICUC.

Evaluation of the Fao‐56 Methodology For Estimating Maize Water Requirements Under Deficit And Full Irrigation Regimes In Semiarid Northeastern Colorado

“…The ICUC, an index proposed by Burt et al . () and discussed by Mateos (), is not widely used in field studies, despite being implemented in catchment‐ or irrigation district‐scale study reported ICUCs of 51–67% (Clemmens, ; Barros et al, ). In our case, high ICUC values were obtained because deep percolation and runoff were negligible due to the high‐frequency irrigation, an irrigation machine with a high uniformity coefficient, the monitoring of SWC to avoid exceeeding FC values, and an irrigation rate that avoided observable runoff.…”

Developing Irrigation Management at District Scale Based on Water Monitoring: Study on Lis Valley, Portugal

“…The monitoring methodology of collective irrigation supply systems followed the methodology presented by [16,27,28], including the observations of operative practices and the measuring of The on-farm assessment of irrigation and drainage practices has great importance when regarding the general improvement of an irrigation district scale [16]. The prevailing dominant irrigation technology in LVID is the surface irrigation [17], by graded furrow or by flooding level basins, applied essentially to fodder maize and permanent pastures.…”

Water balance of irrigated areas: a remote sensing approach

“…As a result, irrigated areas under study should be treated as control volumes, with vertical and horizontal boundaries that are usually challenging to define (Burt et al ., ). Even after determining the appropriate boundaries, it is usually more difficult to accurately identify all of the fluxes that move through them (Clemmens, ). For example, the unmonitored groundwater flow from non‐cultivated highlands and the three major irrigation canals that surround the Violada Irrigation District (VID) in northeast Spain resulted in an average water balance closure of −23% during the study period of 1995 to 1998 (Isidoro et al ., ).…”

“…The accuracy of precipitation measurement also played an important role in determining the accuracy of estimated water consumption. Even though the amount of precipitation was by far smaller than the amount of water diversion, the higher uncertainty (22.4%) of this parameter was responsible for 21% of the error variance in water consumption estimates (Clemmens, ). As it was shown in this study, the accuracy assessment approach developed by Clemmens and Burt () can be successfully applied to identify the major contributors to the uncertainty in the water fluxes that are estimated as the residual of the water balance.…”

“…In order to better understand the partitioning of water fluxes among agricultural, municipal, and industrial sections in the Imperial Valley, Clemmens () also elaborated on the water balance of several IID subsystems, such as irrigation canal, farm, and open drain and river. The uniqueness of performing subsystem water balance analysis lies in the fact that while the scale of study remains at the level of entire irrigation scheme, the analysis is focused only on one element of the system.…”