Modeling land use change impacts on water resources in a tropical West African catchment (Dano, Burkina Faso)

• Published in: Journal of hydrology (Amsterdam) 2016-06, Vol.537, p.187-199
• Main Authors: Yira, Y., Diekkrüger, B., Steup, G., Bossa, A.Y.
• Format: Article
• Language: English
• Subjects: Brackish; Catchments; Computer simulation; Discharge; Hydrology; Land use; Land use change; Land use scenarios; Multivariate evaluation; Urban areas; WaSiM; Water resources
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2016.03.052

•Land use and land cover change over the past 25years was assessed.•Savannah areas are continuously converted to cropland and settlements.•A multivariate validation of a process based hydrological model was achieved.•Land use change potentially affects available water resources and flood risk. This study investigates the impacts of land use change on water resources in the Dano catchment, Burkina Faso, using a physically based hydrological simulation model and land use scenarios. Land use dynamic in the catchment was assessed through the analysis of four land use maps corresponding to the land use status in 1990, 2000, 2007, and 2013. A reclassification procedure levels out differences between the classification schemes of the four maps. The land use maps were used to build five land use scenarios corresponding to different levels of land use change in the catchment. Water balance was simulated by applying the Water flow and balance Simulation Model (WaSiM) using observed discharge, soil moisture, and groundwater level for model calibration and validation. Model statistical quality measures (R2, NSE and KGE) achieved during calibration and validation ranged between 0.6 and 0.9 for total discharge, soil moisture, and groundwater level, indicating a good agreement between observed and simulated variables. After a successful multivariate validation the model was applied to the land use scenarios. The land use assessment exhibited a decrease of savannah at an annual rate of 2% since 1990. Conversely, cropland and urban areas have increased. Since urban areas occupy only 3% of the catchment it can be assumed that savannah was mainly converted to cropland. The conversion rate of savannah was lower than the annual population growth of 3%. A clear increase in total discharge (+17%) and decrease in evapotranspiration (−5%) was observed following land use change in the catchment. A strong relationship was established between savannah degradation, cropland expansion, discharge increase and reduction of evapotranspiration. The increase in total discharge is related to high peak flow, suggesting (i) an increase in water resources that are not available for plant growth and human consumption and (ii) an alteration of flood risk for both the population within and downstream of the catchment.