Water Productivity from Integrated Basin Modeling

It is obvious that real water saving measures are only possible if the current water resources are clearly understood. For a basin in western Turkey, simulation modeling at three different scales, field, irrigation scheme and basin level was performed to obtain all terms of the water balance. These water balance numbers were used to calculate the Productivity of Water (PW) at the three levels. The four performance indicators considered were: PW_irrigated (yield / irrigation), PW_inflow (yield / net inflow), PW_depleted (productivity / depletion), and PW_process (productivity / process depletion), all expressed in kg yield per m³ water. For the two cotton fields considered at the field scale level, the more upstream field performed better than the field at the tail-end. This was partly a result of the difference in climatic condition, but was mainly due to the location of the two fields: upstream vs. downstream. At the irrigation scheme level PW_irrigated was higher than at the individual cotton field, 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 are lower than those at the irrigation scheme, as large areas of the basin were covered with less productive land covers. It is concluded that performance indicators are useful ways of representing water dynamics with clearly understandable numbers, and that it is important to consider all the spatial scales at the appropriate level of detail.