Knowledge of hydrological processes and water balance elements are important for climate adaptive water management as well as for introducing mitigation measures aiming to improve surface water quality. Mathematical models have the potential to estimate changes in hydrological processes under changing climatic or land use conditions. These models, indeed, need careful calibration and testing before being applied in decision making. The aim of this study was to compare the capability of five different hydrological models to predict the runoff and the soil water balance elements of a small catchment in Norway. The models were harmonised and calibrated against the same data set. In overall, a good agreement between the measured and simulated runoff was obtained for the different models when integrating the results over a week or longer periods. Model simulations indicate that forest appears to be very important for the water balance in the catchment, and that there is a lack of information on land use specific water balance elements. We concluded that joint application of hydrological models serves as a good background for ensemble modelling of water transport processes within a catchment and can highlight the uncertainty of models forecast.
Mathematical models are effective tools for evaluating the impact of predicted climate change on agricultural production, but it is difficult to test their applicability to future weather conditions. We applied the SWAP model to assess its applicability to climate conditions, differing from those, for which the model was developed. We used a database obtained from a winter wheat drought stress experiment. Winter wheat was grown in six soil columns, three having optimal water supply (NS), while three were kept under drought-stressed conditions (S). The SWAP model was successfully calibrated against measured values of potential evapotranspiration (PET), potential evaporation (PE) and total amount of water (TSW) in the soil columns. The Nash-Sutcliffe model efficiency coefficient (N-S) for TWS for the stressed columns was 0.92. For the NS treatment, we applied temporally variable soil hydraulic properties because of soil consolidation caused by regular irrigation. This approach improved the N-S values for the wetting-drying cycle from -1.77 to 0.54. We concluded that the model could be used for assessing the effects of climate change on soil water regime. Our results indicate that soil water balance studies should put more focus on the time variability of structuredependent soil properties.
Despite the increasing interest in applying composts as soil amendments worldwide, there is a lack of knowledge on short-term effects of compost amendments on soil structural and hydraulic properties. Our goal was to study the effect of compost and vermicompost-based soil amendments on soil structure, soil water retention characteristics, aggregate stability and plant water use efficiency compared to that of mineral fertilizers and food-waste digestate and examine if these effects are evident within a short time after application. We set up a pot experiment with spring wheat using a sandy and a loamy soil receiving either mineral fertilizer (MF); dewatered digestate from anaerobic digestion of food waste (DG), vermicomposted digestate (VC_DG); sewage sludge-based compost (C_SS) and sewage sludge-based vermicompost (VC_SS). We then monitored and calculated the soil water balance components (irrigation, outflow, evaporation, transpiration, and soil water content). At harvest, we measured shoot biomass, soil texture, bulk density, water retention characteristics and aggregate stability. The irrigation use efficiency (IE) and the plant water use efficiency (WUE) were calculated for each treatment by dividing the transpiration and the dry shoot biomass with the amount of water used for irrigation, respectively. For the sandy soil, we used X-Ray computed tomography to visualise the pore system after applying organic amendments and to derive metrics of the pore-network such as its fractal dimension, imaged macroporosity and critical pore diameter. X-Ray tomography indicated that composting and vermicomposting resulted in more complex and diverse porous system and increased soil macroporosity. The increased fractal dimensions also indicated that compost and vermicompost can contribute to structure formation and stabilization within a short time after their application. Despite the small application rate and short incubation time, the application of organic amendments to the two different soil types resulted in improved soil water holding capacity and water use efficiency. Composting and vermicomposting appeared to have the best effect at reducing the irrigation demand and evaporation losses and increasing the water use efficiency of the plant, likely through their effect on soil structure and the pore-size distribution.