Calculation of Water Demand for Multiple Uses in a Specified Region Using a SWAT Model

Abstract

The calculation of water demand for multiple uses including the irrigation of crops and municipal uses in a specified region is an essential and urgent task for sustainable water management in such regions. To achieve the aim of this study, the Soil Water Assessment Tool (SWAT) was used with the aid of a Geographic Information System (GIS). The region of Jilawia and Muharam, which lies North of Babylon in Iraq, was selected as a case study so that the water available and demand for that water could be calculated. This region is irrigated from the Great Al–Mussiab Project out to a 12 km radius, covering a 20000 dunum (50 kM2) area, as well as receiving rainfall water. Four types of seasonal crops, Rice, Corn, Wheat, and Cucumbers, are grown, and several residential units have been suggested as planned investment projects in the region of study which will also need sufficient available water. The results of the simulation model in the SWAT covered the period from 2010 to 2020. The Curve Number (CN) and the surface runoff of the region were both calculated, and the SWAT model calibrated against the measured reference evapotranspiration. The results of this calibration were somewhat convergent, demonstrating an error of 12.5%. The results of the calculation of water available and demand showed that sufficient water is available for only municipal uses for 2,300 persons, fulfilling the full capacity of the investment projects, with a deficit of water more generally appearing where both irrigation and municipal use are taken into account. These deficits are 154.70%, 68.97%, and 11.53% with Rice, Corn, and Cucumber crops respectively; however, there is a surplus of water of 34.13% with a Wheat crop. The results also showed that the area of the study region could support 39.25%, 59.17%, and 89.65% of the total available area being turned to Rice, Corn, and Cucumber crops, respectively, to achieve the planned investment projects. SWAT is shown to be an appropriate time saving tool for calculating water demand for multiple uses in a specified region. It can also be concluded that Jilawia and Muharam is a suitable region for the planned investment projects, including managed agriculture and municipal projects, based on the available water in this region.