Spatiotemporal relations between water budget components and soil water content in a forested tributary catchment

We examined 3 years of measured daily values of all major water budget components (precipitation P , potential evapotranspiration PET , actual evapotranspiration ET , and runoff R ) and volumetric soil water content θ of a small, forested catchment located in the west of Germany. The spatial distribution of θ was determined from a wireless sensor network of 109 points with 3 measurement depths each; ET was calculated from eddy‐covariance tower measurements. The water budget was dominantly energy limited, with ET amounting to approximately 90% of PET , and a runoff ratio R/P of 56%. P , ET , and R closed the long‐term water budget with a residual of 2% of precipitation. On the daily time scale, the residual of the water budget was larger than on the annual time scale, and explained to a moderate extent by θ ( R 2 = 0.40). Wavelet analysis revealed subweekly time scales, presumably dominated by unaccounted fast‐turnover storage terms such as interception, as a major source of uncertainty in water balance closure. At weekly resolution, soil water content explained more than half ( R 2 = 0.62) of the residual. By means of combined empirical orthogonal function and cluster analysis, two slightly different spatial patterns of θ could be identified that were associated with mean θ values below and above 0.35 cm 3 /cm 3 , respectively. The timing of these patterns as well as the varying coherence between PET , ET , and soil water content responded to changes in water availability, including a moderate response to the European drought in spring 2011.