Determination of Yazd-Ardakan watershed water balance by using Thornthwaite- Mather method and application of distributed rainfall-runoff model

In this research, the long-term monthly water balance of Yazd-Ardakan watershed, with an area 16000 km2, was developed based on Thornthwaite–Mather method in GIS. Model input data included the monthly maps of temperature, precipitation, and soil water holding capacity in roots with a cell size of 60 m, and model output included monthly maps of actual evapotranspiration, map of soil water storage, the lack of moisture and excess water, determined by Ilwis software. Results showed that more than 80% of rainfall exited the watershed as evapotranspiration, approximately 8% as surface runoff, and the rest as subsurface runoff in the study area. The amount and area of groundwater recharges varied between 20-50% in different months.Groundwater recharge occurred only in December to March, whose value varied between. 5 mm in December to 17 mm in January.