Markus C. Casper

Fuzzy logic-based rainfall-runoff modelling using soil moisture measurements to represent system state

Abstract Initial catchment state, such as soil moisture, strongly controls rainfall—runoff transformation processes. However, due to the high spatial and temporal variability of soil moisture, point measurements may not always be suitable to represent the actual system state of a whole catchment as required in distributed catchment modelling. In this study a fuzzy rule-based system (FRBS) using the Takagi-Sugeno-Kang approach has been developed using soil moisture and rainfall as input variables to predict the actual discharge at the catchment outlet. Four soil moisture probes from the hydrological test site Dürreych (Black Forest, southwest Germany) were selected, each of them representing a particular runoff generation process (saturation excess flow, infiltration excess flow, slow and fast interflow, return flow). After manual calibration, the simulated peak discharges were very similar to the measured values. Furthermore, the pattern of rule activation in the FRBS reflected the complex, highly nonlinear behaviour of the catchment. Thus, in the FRBS framework, the measurements of soil moisture at representative locations could be used as representation for the actual system state, allowing for an entirely data-driven prediction of the runoff response using rainfall.

Temporal changes in soil water erosion on sloping vineyards in the Ruwer- Mosel Valley. The impact of age and plantation works in young and old vines

Abstract It is well known that rainfall causes soil erosion in sloping German vineyards, but little is known about the effect of age of plantation on soil erosion, which is relevant to understand and design sustainable management systems. In the Ruwer-Mosel valley, young (1- to 4-years) and old (35- to 38-years after the plantation) vineyards were selected to assess soil and water losses by using two-paired Gerlach troughs over three years (2013-2015). In the young vineyard, the overland flow was 107 L m-1 and soil loss 1000 g m-1 in the year of the plantation, and decreased drastically over the two subsequent years (19 L m-1; 428 g m-1). In the old vineyard, soil (from 1081 g m-1 to 1308 g m-1) and water (from 67 L m-1 to 102 L m-1) losses were 1.2 and 1.63 times higher, respectively, than in the young vineyard.

Spatial pattern and temporal variability of runoff processes in Mediterranean Mountain environments - a case study of the Central Spanish Pyrenees

Mediterranean mountain environments like the Central Spanish Pyrenees show a highly variable rainfall-runoff response, mainly explained by the intense intra- and inter-annual variability of precipitation yield. This leads to a highly differentiated moisture status and therefore it is assumed to lead also to highly variable runoff contributing areas. For the identification of areas with certain dominant runoff processes in an experimental headwater catchment in which agriculture was abandoned several decades ago the concept of the topographical index was extended by means of weighting grids. These weighting rasters were generated using additional information on soils and vegetation. Runoff generating areas were identified widespread in the catchment, with Hortonian overland flow (HOF) dominating the runoff processes on degraded soils, and saturation overland flow (SOF) dominating the footslope areas, where hydromorphic soils were mapped. Rainfall-runoff experiments were performed to quantify runoff and erosion and to identify seasonal changes using experimental data gained in different seasons of the year. The seasonal changes in runoff response could be localised clearly within the areas of SOF, whereas the other ones showed a similar behaviour. This implied that the procedure of delineation had to be differentiated for dry and moist conditions, and that the SOF areas had to be reclassified as SSF/DP areas for dry conditions. Due to the location of these areas close to the ravine, we could explain the pronounced switching runoff behaviour of the catchment. GIS techniques combining different levels of topographic, soil and vegetation information showed to be suitable for delineation of areas with different runoff generation processes. The inclusion of seasonally distributed experimental data demonstrated that for dry conditions, slightly different methods have to be applied. Nevertheless, the study showed also the limitations of the combined methods: (I) subsurface flows and ground water recharge could only be deduced, not demonstrated, (II) finally, there is still a good knowledge of the area needed for an accurate process representation.

Application of Bayesian Decision Networks for Groundwater Resources Management Under the Conditions of High Uncertainty and Data Scarcity

This paper presents management of groundwater resource using a Bayesian Decision Network (BDN). The Kordkooy region in North East of Iran has been selected as study area. The region has been sub-divided into three zones based on transmissivity (T) and electrical conductivity (EC) values. The BDN parameters: prior probabilities and Conditional Probability Tables - CPTs) have been identified for each of the three zones. Three groups of management scenarios have been developed based on the two decision variables including “Crop pattern” and “Domestic water demand” across the three zones of the study area: 1) status quo management for all three zones represent current conditions; 2) the effect of change in cropping pattern on management endpoints and 3) the effect of future increased domestic water demand on management endpoints. The outcomes arising from implementing each scenario have been predicted by use of the constructed BDN for each of the zones. Results reveal that probability of drawdown in groundwater levels of southern areas is relatively high compared with other zones. Groundwater withdrawal from northern and northwestern areas of the study area should be limited due to the groundwater quality problems associated with shallow groundwater of these two zones. The ability of the Bayesian Decision Network to take into account key uncertainties in natural resources and perform meaningful analysis in cases where there is not a vast amount of information and observed data available – and opportunities for enabling inputs for the analysis based partly on expert elicitation,emphasizes key advantages of this approach for groundwater management and addressing the groundwater related problems in a data-scarce area.

Reliability of inversely reconstructed soil moisture profiles and consequences for field applications.

The so called Spatial-TDR system allows a monitoring of transient soil moisture profiles. Using a fast inversion algorithm it is possible to reconstruct the electrical properties along a probe in homogenous materials. To evaluate the ap- plicability of the Spatial-TDR under field conditions different laboratory experiments were carried out in this study. The measurements were made with 60 cm long three-rod probes. A changing water table has been simulated in soil columns filled with homogeneous and layered silt and sand. Besides the impact of the soil heterogeneity the effect of a changed probe geometry and an air gap along the probe were investigated. For straight probes with good soil contact the reconstructed soil moisture values were very reliable for the homogeneous and layered soil profile. However, the reconstruction algorithm does not cope with discrete changes of impedance along the probe resulting in strong oscillations in the reconstructed moisture profiles. The failure is due to the rather flat edge of the TDR input signal and can not be detected by the optimization approach yet. Discrete changes of the impedance lead to an increasing oscillation of the capacitance that nevertheless give a very good simulation of the TDR waveform. Alto- gether, the Spatial-TDR measurement system may be very useful to capture temporal and spatial soil moisture dynamics down to 50 cm depth. The main advantages are the high temporal and spatial resolution. However, it requires further de- velopment if one wants to capture accurate absolute soil moisture values.

Studying Parameter Sensitivity and Behaviour of the Crop Model STICS

The present article shows the results of a study on the soil module of the STICS (Simulateur Multidisciplinaire des Cultures Standards, developed by INRA, France) crop model. Simulation models are often applied to regions where conditions are substantially different from the ones which the model was originally developed for and validated against. This was the reason to study the sensitivity of the STICS soil module and to analyze model behavior with regard to spatial transferability. The model was parameterized with data collected from an area close to the German city of Trier. Using this parameterization as a baseline, an initial study was carried out on the sensitivity of the soil parameters. This was followed by an analysis of model behavior concerning parameters which also in the real system are responsible for successful or poor plant growth. This provided some improvements over the initial simulation results. However, the model failed to match the real systems behavior concerning yield, biomass development, and root growth. From various approaches to parameterization it has become clear that a high level of abstraction is required to produce a satisfactory model of the soil-plant-atmosphere continuum and in particular the soil water dynamics. This applies especially to extreme locations as well as to relatively extreme climatic years.

Separation of Stormflow Hydrographs in Surface and Subsurface Flow by Perceptual Based Modelling of Channel Inflow Components

The aim of this case study was to determine the origin of stormflow runoff in a 31 ha headwater basin in Western Germany. Therefore, the contribution of infiltration excess and saturation overland flow as well as matrix and preferential flow has been assessed along a deeply incised channel of 300 m length. Measurable parameters and simple al- gorithms were used to assess the flow rate of the different runoff components. Only the scaling parameter cf that repre- sents converging flow processes and controls the actual height of the saturated zone along the channel incision has been calibrated. The results showed that during wet conditions the subsurface flow rates exceed the surface flow rates tremen- dously. In contrast, for the short but intense summer storm the hydrograph consists solely of surface runoff components. Obviously, the parameter cf accounts for the pre-event condition of the catchment. This leads to the conclusion, that the extension of the contributing subsurface space mainly governs stormflow processes. Further investigations shall focus on the relationship between subsurface flow processes and the lateral and vertical extension of the saturated zone.