Analysis of land use changes and water resources in lowland catchments of Northern Germany
With increasing pressures from natural disturbances and anthropogenic activities, water quality is degraded and sustainable management becomes more challenging. A good understanding of the key influential factors for water resources will help to develop effective catchment management plans for addressing water resources issues. However, a systematic assessment of cause-effect relationships between land use and water quality or quantity is still rare, particularly across different temporal and spatial scales. This study aims to explore the spatially distributed catchment variables controlling landscape patterns, and to identify the important catchment characteristics and spatial scales for explaining the water quality or quantity dynamics. The rural lowland catchments (namely Kielstau and Stör) in Northern Germany were selected as study areas. Intensive field campaigns have been carried out in the two catchments: land use mapping in both catchments and a water quality campaign (2018-2019) in the Stör catchment that complements campaigns from 1992-1994 and 2009-2011. Different multivariate statistics and a hydrological modelling (SWAT) approach have been applied. The distribution patterns of each specific land use class were identified based on logistic regression analysis using spatially distributed variables. Furthermore, stepwise multiple linear regression (SMLR) and redundancy analyses (RA) were applied to investigate influences of main categories of catchment characteristics on water quality at multiple spatial and temporal scales. The SWAT model was calibrated and validated for modeling the dynamic processes of streamflow, sediment, total phosphorus (TP), and total nitrogen (TN). The variabilities in main water balance components and nutrients in response to varied landscape patterns were investigated by applying the integrated approach of SWAT modeling and partial least squares regression model (PLSR).