Evaluation of land use from the point of water yield within the Bartin-Kirazliköprü dam watershed

Bartin-Kirazlıköprü Dam construction was initiated in 1999 and is still going on construction. Dam watershed aims to collect approximately 865 km2 Bartın Stream watershed's water and this dam watershed, constitutes almost half of the Bartın Stream Watershed. Dam watershed involves Ovacuma Stream and its' tributaries and a large part of the Ulus Stream. About half of the dam watershed is covered by forests and more than one-third of the watershed is covered with agricultural areas. The remaining parts of the watershed respectively constitute; rural settlements, deforested forest soil, sand dunes, service areas and rocks. In this study, land uses in the watershed were investigated in terms of dam water yield. Suitability and misuses of land were evaluated around this concept. In this context, the elevation of the watershed ranges between 60 and 1600 m. This broad elevation was divided into 100 m altitudinal sub-gradients using the Geographic Information Systems (GIS) tools. Water balance of each altitudinal sub-gradient has been calculated using the Thornthwaite method. According to the results of this study, agricultural areas cover in average 46% within the first 600 m altitudinal gradients of the watershed. However the agricultural areas diminish about 10% at each 100 m gradient covering 17%. These areas are close to the upland settlements within the watershed. These rural settlements are located close to the agricultural areas and cover about 5% of the watershed. On the other hand, forests cover 28% of the first 200 m altitudinal gradients and the deciduous stands constitute the largest portion of these forests. The forest areas dominate almost 50% of the altitudinal gradients between 200 and 600 m. Within 1000m, these forest areas cover 90% ratio. The rest of the zone is covered by the agricultural areas. Up to 1200 m altitudinal gradient, deciduous stands constitute the largest portion of the forests. Within next altitudinal gradients, coniferous stands are located. Within the altitudinal gradients of 1000 and 1100 m, the rate of the agricultural areas diminish about 3%. Besides, up to 1600 meters, agricultural areas almost not exist. Particularly at the altitudinal sub-gradients from 1100 m to 1600m, the forest areas dominate. Dependent upon the increasing altitude in the watershed, reduced precipitation and increased temperature led to the evapotranspiration rate be reduced by about half. On the other hand, based on the calculation which also considers land use, the evapotranspiration rates were about 5% higher than that of the raw calculation. Altitude and forest cover play an important role in the increment of the evapotranspiration rate. In this study, analysis of the current land use status of a mesoscale dam watershed which was quite significant in terms of water cycle and balance may contributed to the sustainable dam watershed planning. Key Words Dam watershed, land use, altitudinal gradients, water balance.