Rain-gauge density assessment in Golestan province using spatial correlation technique

Rain-gauge networks are often installed to provide measurements that characterize the temporal and spatial variations of rainfall، thus accurate and efficient design of them are necessary. The main objective of this research is to evaluate the rain gauge network installed and administered by the Ministry of Energy in the Golestan province (39 rain gauge stations during 12 years)، using spatial correlation technique. Considering the effects of topography on precipitation pattern، the Golestan province has been divided into two homogeneous areas. In each area the correlation functions based on correlation between monthly rainfall data and distances of stations have been determined and the accuracy of spatial rainfall estimation with the running rain gauges have been evaluated using two accuracy criteria (Ac1 and Ac2). Then، depending on the desired level of accuracy، the required number of rain gauges and their distances and spatial pattern were estimated in both homogeneous areas. Results showed that the present network of rain gauges in the mountainous area has more suitable spatial pattern than the flat area. Also it has been concluded that the existing network of rain gauges would suffice the objectives of management and research studies that require data with 10 to 15% accuracy level. However، in case of need for more accurate estimation of spatio-temporal variations of rainfall، the number of rain gauges in the mountainous area should be increased. While، in the flat area relocation of existing rain gauges is necessary.