Changes in irrigated land and agricultural water use in the Lake Urmia basin

In the Urmia basin, intensive agriculture relies heavily on irrigation systems using river-fed irrigation canals and groundwater-supplied pressure systems, causing Lake Urmia to shrink in recent years. The loss of lake area has diminished the productivity of surrounding agricultural lands and caused environmental out-migration and substantial economic losses. Because water resources in the Lake Urmia basin are limited, the government has prohibited new development plans and determination of new water rights. In this study, remote sensing, geographic information systems, and data gathered from official organizations were used to quantify the change in area under irrigation and water consumption. Multi-date Landsat Thematic Mapper imagery was employed to derive the land use map. The study was conducted in the Miandoab alluvial plain, a 1025 km(2) area in the southeast part of the Lake Urmia basin, located in northwest Iran. Crop data gathered from field observations were used to verify the land cover map. To quantify the change in agricultural water use, the net irrigation water requirements for each crop were determined using the CROPWAT model, and the reference evapotranspiration was estimated using the Penman-Monteith equation. The results of this study indicated a 19,363 ha increase in total irrigated area (approximate to 20%) and a 226 million cubic meter increase in water demand (approximate to 35%) for irrigation during the study period. This research highlighted the role of integrated water resources management as a framework to develop the agricultural lands in the basins.