GroMoPo Metadata for Nishapur Plain model

In Iran, due to arid and semi-arid climate, groundwater resources play an essential role in food production, as well as domestic and industrial water supply. In recent years, increasing population, scarcity of surface water resources, and effects of worldwide and regional climate change have resulted in over-exploitation and unsustainability of these resources in the country. The present study aims to estimate groundwater sustainable yield, examine effects of spatial and temporal scale, and propose a plan for groundwater sustainable use in Nishapur Plain, in the north-east of Iran. In investigating the effects of spatial scale, the area of the plain is divided into several zones, with estimation of groundwater recharge and discharge for each zone and the temporal scale refers to the different time-scales used to estimate the average value of groundwater recharge and discharge. The results of the transient groundwater model of Nishapur Plain, revealed that average annual groundwater storage depletion is about 311 MGM(1) during the 8-year period of 2005-2013 with the minimum, average, and maximum water table decline of 0.6 m, 7.7 m and 11 m, respectively. The study results suggest that sustainable yield is closely correlated to the spatial and temporal scales, and refinement of spatial and temporal scales increases sustainable yield from 39 % to 59 % of the current pumping volume equal to about 100 MCM of water (or 8000 ha of irrigated land). Furthermore, when the groundwater withdrawals are limited to sustainable yield, increasing irrigation efficiency from 38 % (current efficiency) to about 60 %, can potentially result in maintaining irrigated areas and minimize adverse social and economic impacts of limiting groundwater usage. This is an achievable rate, based on data from the Iranian government organizations. The results of this study can be extended to other semi-arid agricultural areas, which primarily depend on groundwater.