Title: Impact of change in land use and seasonality on river water quality in the Rur catchment, Germany
Author: Sristika Adhikari
Supervising Institution: IHE Delft - Institute for Water Education
Land use change is the process of transforming one (natural) landform into another type of land. It is frequently done to increase the economic value of land which might cause ecological detriment. The Rur catchment also has over time undergone land use change which could have affected the hydro-chemical processes of the river. Three sub-catchments in the Rur, Upper Rur, Inde and Wurm currently have different kinds of land use. Upper Rur is more natural catchment, Inde is mixed type and finally Wurm is highly modified by anthropogenic activities. Surface runoff of a place is also influenced by the land use from which it passes. So, this study investigated how land use and seasonal variation influence water quality variables (nutrients, physico-chemical parameters, DOM and anions) in these three different catchments. Since temporal change in land use activities affects the river water quality, this study also measured the land use change of these three catchments from 2000 to 2018. Land cover images from Coordination of Information on the Environment (CORINE) were used and analysed in QGIS environment to calculate areas of different land uses in each catchment. In situ measurements were done for physico-chemical parameters (pH, EC, DO and temperature). Laboratory analysis was undertaken to measure concentrations of DOC, nutrients (NO3-N, SiO2, PO4-P, NH4-N) anions (SO4 and Cl). Historical water quality data were collected from the online public source provided by Ministry of Environment and Nature conservation from Germany. R-software was used for statistical analysis and graphical presentation. Key results of the study show significant variation of NO3-N, SiO2, PO4-P, SO4, Cl, TN, EC, temperature, (ß:ᾳ), FI and BIX among three catchments. Seasonal variation of these variables was also significant. Most of the water quality variables showed positive significant relation with distance from origin of the stream in all three catchments. In the Inde and Wurm water quality variables showed positive significant relation with percentage of urban land and agricultural area. Land use change mapping found little change in the Upper Rur between 2000 to 2018. But in the Inde and Wurm decrease in agricultural land and associated increase in industrial, commercial and urban land was found. Increase in mining area in the Inde enhanced SO4 and EC. Study of spatial variation of water quality did help to understand the influence of land use and seasonality on river water. Conversion rates of natural to human dominated land use could be quantified in this study through land use change mapping, which further helps in making water management plan for these and comparable German and European catchments. However high quality historical data set is a key requirement to maximize the output in process of relating impact of land use change in water quality.