Hydrological study of the Wadi Jarf basin using Geographic Information Systems

Abstract

The study of this research is to obtain the hydrological study of Wadi Jaref Basin, which is located in Sirt area—in the centre of Libya. This study is achieved by the analysis of the basin's morphometric features which are included area, shape relief properties, and the network of the streams orders, and in addition to the analysis of hydrological features by using the technology of Geographic Information Systems (GIS) and depending on the Digital Elevation Model (DEM),The aims of the study is  to identify the importance of area, shape, and topographic features and the orders of valley (Wadi Jaref), to build a database for them, and to show their effect on the hydrology of the basin. The study also aims to analyze hydrological features which is represent by the volume of runoff, the concentration of time, lag time, flow velocity, and the rush of discharge, The methodology of this study depends on integrating the regional approach which relies on analytical and statistical methods, using many mathematical equations. The results showed that, the area of the basin is 2,519.81 km², which is showed a huge area, with a length of perimeter 341.69 km and a basin length from the farthest point to the outlet reach to 103 km. The shape of the basin tends to be more towards elongation than circularity, with a circularity ratio of 0.271 and  an elongation ratio of 0.55. The slope average reached to  2.9 meters per kilo, These features ( areal, shape), and topographic characteristics had an important effect and impact on the hydrological features in terms of the (timing and volume) of water flow. The surface runoff volume reached to  0.021 billion cubic meters, represent 4.38% of the total rainfall over the basin. The concentration of time was 21 hours, the lag time was 12.6 hours, and the velocity of  flow  was 4.9 m³/hour, which reflected  the basin’s slow response to rainfall due to its huge  area and low relieif, The network of drainage contains six streams orders, including 3,429 watercourses with a sum  length of 3,343.9 km. The basin reached to an advance stage of the erosional cycle, called  the old age stage, as pointed  by the hypsometric integral value of 29.18. The study summarized that, the risk of flooding in the valley of Wadi Jaref Basin is low and the syudy  recommended to benefit from these results, especially in the management of water resources and agricultural.