Operational management of agricultural bore wells in paddy fields

In this research, an operational simulation model was developed to indicate the importance of agricultural bore wells as an irrigation water resource and sustainable management of them to supply irrigation demand of paddy fields. The main approach of this research was based on maximum using of local water resources (e.g. wells, ponds). In the proposed model, crop evapotranspiration, irrigation requirement and interval and water head in soil and bore well are daily calculated based on input data and simulation equations. Then, using of obtained irrigation scheduling and considering the limitation of minimum permission level in bore well, water harvesting days from bore well, pumping discharge and time, pond water in fields and runoff are calculated. Simulation of groundwater level fluctuation in the out of paddy rice growing season in unsaturated condition of soil was computed by Hydrus-1D. The model was run for paddy fields of Rasht Rice Research Institute for normal year; The results indicated that 10 irrigation events were required that six and four of them were supplied by bore well and canal, respectively. The obtained results in the studied paddy fields showed that shallow groundwater level was discharged by precipitation in the out of paddy rice growing season and raised from depth of 4.85 m to 1.82 m. Therefore, operation of bore wells during paddy rice growing season as well as considering minimum permission water head does not cause considerable groundwater drawdown and unsustainable operation