Impact of land use change on water availability in Indonesia under varying climatic conditions

Land use changes such as deforestation and conversion of agricultural lands influence the hydrology of catchments and hence water availability and demand. In Indonesia, deforestation and development of agricultural lands and palm oil plantations have resulted in land use changes at different scales. These land use changes have affected the hydrology and water availability as reflected by for instance the increased number of floods in the Solo catchment in Central Java and the more uneven distribution of river discharge throughout the year in the Katingan catchment in Central Kalimantan. To restore the balance of water availability between upstream and downstream areas within a catchment and between the dry and wet season, land use management can be used as a measure to distribute the water more evenly. Models are very useful in evaluating the effectiveness of spatial measures on the spatial and temporal distribution of water. This project will assess the effects of different land use configurations on the spatial and temporal distribution of water for two catchments in Indonesia (Solo and Katingan) serving as exemplary examples of catchments where past land use changes have significantly affected hydrology and future changes are expected to enhance these impacts. In addition, the Bogowonto catchment in Central Java, where a reforestation program is successful at the landscape level, will be used as a model to test whether restoring non-forest to forest has already contributed to a more water resilient system. As a first step, dominant hydrological processes in the catchments will be identified based on data analysis and local field studies. In the second step, for each catchment a spatially distributed hydrological model will be set-up incorporating the dominant hydrological processes. This model will be calibrated and validated using multiple variables and multiple objectives at multiple scales in the third step. In the final and fourth step, the hydrological model will be applied to the project catchments to assess the impacts of different land use patterns on the distribution of water within the catchment and between the different seasons taking climatic variability into account. Outcomes of this project will be translated to results and lessons at the level of local stakeholders and governments. This should lead to improved land use management resulting in catchments which are able to deal with varying water availability and demand at different temporal and spatial scales being robust and sustainable water systems.