Simulation modeling at different scales to evaluate the productivity of water

With the increasing scarcity of water and the need for real water saving me asures, a clear understanding of the productivity of water is essential. Fo r a basin in western Turkey, simulation modeling was performed at three dif ferent scales (field, irrigation scheme, and basin level) to obtain all ter ms of the water balance, These water balances were used to calculate the Pr oductivity of Water (PW) at the three levels. Four PW indices were consider ed: PWirrigated (yield / irrigation), PWinflow (yield / net inflow), PWdepl eted (yield / depletion), and PWprocess (yield / process depletion), all ex pressed in kg yield per in water. Two cotton fields were considered at the field scale and it was found that the more upstream field performed better than the field at the tail-end since runoff from the upstream field was use d by downstream users and was not considered as a loss. At the irrigation s cheme level PWirrigated was higher than at the individual cotton Field leve l, since non-irrigated crops were also included, Other PW values were lower as crops more sensitive to drought were also found in the irrigated areas. Basin scale PWs were lower than those at the irrigation scheme, as large a reas of the basin were covered with less productive land types. This study demonstrates that the PW indices provide quantitative measures of water dyn amics. Models provide a useful methodology for extending field observation for the estimation of the indicators. (C) 2001 Elsevier Science Ltd. Ail ri ghts reserved.