EVALUATION AND MANAGEMENT OF WITHDRAWAL GROUND WATER FOR AGRICULTURE IN NIHM DIRECTORATE-YEMEN

The aim of this research was to evaluate and manage ground water withdrawal for agriculture in Nihm directorate, by studying random sample to measure and read the requirements data of agricultural Nihm wells. Annual ground water withdrawals for agricultural irrigation were compared with both of annual renewable ground water and actual crops water requirement in Nihm. Actual crops water requirements and irrigation scheduling, and quantity of water to be applied using surface and drip irrigation systems were done depending on each data of; Nihm climate, crop coefficients and soil type by using a computer program (FAO). The results showed – as sample:- that the annual volume of groundwater recharge was 21.813 MCM per year, while annual withdrawals volume of groundwater from all agricultural wells was found more than59 MCM per year for irrigating only 3118 ha. Thereby annual withdrawals of ground water was 270% the renewable

groundwater, so annual decreasing  rate of ground water level was found 0.3 m/year. In about 47% of Nihm wells the in-betweens distance among them were below 500m, Where, the distance average among wells in all directions was 560m. The total quantity of groundwater withdrawals for agricultural irrigation increase by 45% (26.4MCM) comparing by actual irrigation requirements calculated for cultivated crops in Nihm (about 32.57MCM) under surface irrigation system (60%efficiency). In addition, results shows that each one hectare receive 18922m3/year of withdrawal groundwater, as about 200% average actual irrigation required to irrigate one hectare by surface irrigation system or 250% average actual irrigation required to irrigate one hectare by modern irrigation systems. If drip irrigation system was applied with efficiency of 90% in substance to surface irrigation system to irrigate qat and grape, and also, if sprinkler irrigation system was applied in substance to surface irrigation to irrigate wheat, so the actual irrigation water required and withdrawal form groundwater will decreases from 32.57MCM/year to 22.887MCM/year, this resulting in saving 36.118MCM/year (62% of the annual groundwater withdrawal).