Changes in Sediment and Water Yield Downstream on a Small Watershed

Effects of dynamic land use/land cover change on water resources and sediment yield in the Anzali wetland catchment, Gilan, Iran

Land use/land cover (LULC) changes strongly affect catchment hydrology and sediment yields. The current study aims at analyzing the hydrological consequences of dynamic LULC changes in the Anzali wetland catchment, Iran. The Soil and Water Assessment Tool (SWAT 2012) model was used to assess impacts on evapotranspiration, water yield, and sediment yield. Two model runs were performed using static and dynamic LULC inputs to evaluate the effects of LULC change between 1990 and 2013. For the static model, the LULC map of 1990 was used, whereas for the dynamic model, a gradual change of the LULC distribution was interpolated from 1990, 2000, and 2013 LULC data. The major LULC changes were identified as an increase of agricultural area by 7% of the catchment area and a decrease of forest coverage by 6.8% between 1990 and 2013. At the catchment scale, the differences in the long-term mean annual values for the main water balance components and sediment yield were smaller than 10 mm (<2.8%) and 3 t/km² (<2.6%), respectively. However, at the sub-basin scale the increase of agricultural land use resulted in an increase of evapotranspiration, water yield, and sediment yield by up to 8.3%, 7%, and 169%, respectively, whereas urban expansion led to a decrease of evapotranspiration, water yield, and sediment yield by up to -3.5%, -2.3%, and -9.4%. According to the results of the monthly time scale analysis, the most significant impact of LULC changes occurs during the dry season months, when the increase of irrigation agriculture results in an increase in water discharge and sediment loads to the Anzali wetland. Overall, the results showed that the implementation of dynamic LULC change into the SWAT model could be adopted as a planning tool to manage LULC change of the Anzali wetland catchment in the future.

Analysis of landscape changes as an indicator for environmental monitoring

Mediterranean coastal landscapes are complex systems that are subject to rapid and extensive changes due to unprecedented human interference. Changes in these landscapes are strong indications of anthropogenic disturbances that should be monitored carefully in order to make effective management decisions. Landscape changes can be analyzed using many qualitative and quantitative techniques. In this respect, the importance of land cover information arises from the fact that any change in the composition and/or configuration of land cover can be used as a landscape-level environmental indicator. Therefore, proper understanding of spatial and temporal characteristics of this environmental attribute is of vital importance as it enables decision-makers to reveal causes of environmental issues and to cope with consequences of mismanagement. The aims of this paper are to analyze landscape-level changes using the largest patch index (LPI) as a simple pattern indicator and provide guidelines for studying change phenomena that take place in the Mediterranean coastal areas. In this respect, changes in the LPI values for agricultural and built-up areas in three different sites were analyzed using georeferenced Ikonos and Quickbird images. The concepts of pattern and process were highlighted as important indicators for studying landscapes and understanding their change.