Analysis of the spatial variation in the parameters of the SWAT model with application in Flanders, Northern Belgium

International audienceOperational applications of a hydrological model often require the prediction of stream flow in (future) time periods without stream flow observations or in ungauged catchments. Data for a case-specific optimisation of model parameters are not available for such applications, so parameters have to be derived from other catchments or time periods. It has been demonstrated that for applications of the SWAT in Northern Belgium, temporal transfers of the parameters have less influence than spatial transfers on the performance of the model. This study examines the spatial variation in parameter optima in more detail. The aim was to delineate zones wherein model parameters can be transferred without a significant loss of model performance. SWAT was calibrated for 25 catchments that are part of eight larger sub-basins of the Scheldt river basin. Two approaches are discussed for grouping these units in zones with a uniform set of parameters: a single parameter approach considering each parameter separately and a parameter set approach evaluating the parameterisation as a whole. For every catchment, the SWAT model was run with the local parameter optima, with the average parameter values for the entire study region (Flanders), with the zones delineated with the single parameter approach and with the zones obtained by the parameter set approach. Comparison of the model performances of these four parameterisation strategies indicates that both the single parameter and the parameter set zones lead to stream flow predictions that are more accurate than if the entire study region were treated as one single zone. On the other hand, the use of zonal average parameter values results in a considerably worse model fit compared to local parameter optima. Clustering of parameter sets gives a more accurate result than the single parameter approach and is, therefore, the preferred technique for use in the parameterisation of ungauged sub-catchments as part of the simulation of a large river basin. Keywords: hydrological model, regionalisation, parameterisation, spatial variabilit

Soil loss prediction using universal soil loss equation (USLE) simulation model in a mountainous area in Aglasun district, Turkey

Land degradation and soil loss is a global event. Human induced pressures on the natural ecosystems are still in progress as well as conservation efforts. The need for sufficient knowledge and data for decision makers is obvious hence the present study was carried out. The study area, the Alasun district, is in the middle west of Turkey and is characterized by a cold and sub-humid Mediterranean climate. The mountainous area is mostly covered with average low canopy closure of 11 - 40% of different forest species (52% of the study area). Universal soil loss equation (USLE) simulation model was used to predict the soil loss amounts in the study area. The results show that the predicted average soil loss amount is 7.38 (ton/ha/year). The average soil depth is about 35 cm and the soil loss tolerance limit is widely exceeded in the study area

Effects of watershed and riparian zone characteristics on nutrient concentrations in the River Scheldt Basin

International audienceThe relative influence of a set of watershed characteristics on surface water nutrient concentrations was examined in 173 watersheds within two subcatchments (Upper-Scheldt and Nete) of the River Scheldt Basin (Flanders, Belgium). Each watershed was described by seasonal rainfall, discharge loading of point sources, morphological characteristics (area, average slope, drainage density, elongation), land use and soil properties (soil texture and drainage). Partial regression analysis revealed that soil drainage variables had the strongest influence on nutrient concentrations. Additional influence was exerted by land use and point source loading variables. Nitrate concentrations were positively correlated with effluent loadings coming from wastewater treatment plants and with the area of agricultural land. Phosphate concentrations were best explained by effluent loadings of industrial point sources and by the area of urban land. Land use close to the river was not a better predictor of nitrate and phosphate concentrations than land use away from the river. This suggests that the mediating impact of riparian zones is rather explained by the hydrologic pathways within the buffer strip

Использование метода моделирования ситуаций при обучении студентов вуза английскому языку

В статье описывается опыт проведения занятий по английскому языку у студентов второго курса направления "Горное дело" с использованием современного активного метода обучения case study. Отмечаются преимущества применения технологии моделирования ситуации при преподавании профессионально-ориентированного курса английского языка в вузе

An integrated approach shows different use of water resources from Mediterranean maquis species in a coastal dune ecosystem

An integrated approach has been used to analyse the dependence of three Mediterranean species, A. unedo L., Q. ilex L., and P. latifolia L. co-occurring in a coastal dune ecosystem on two different water resources: groundwater and rainfed upper soil layers. The approach included leaf level gas exchanges, sap flow measurements and structural adaptations between 15 May and 31 July 2007. During this period it was possible to capture different species-specific response patterns to an environment characterized by a sandy soil, with a low water retention capacity, and the presence of a water table. The latter did not completely prevent the development of a drought response and, combined with previous studies in the same area, response differences between species have been partially attributed to different root distributions. Sap flow of A. unedo decreased rapidly with the decline of soil water content, while that of Q. ilex decreased only moderately. Midday leaf water potential of P. latifolia and A. unedo ranged between 122.2 and 122.7MPa throughout the measuring period, while in Q. ilex it decreased down to 123.4MPa at the end of the season. A. unedo was the only species that responded to drought with a decrease of its leaf area to sapwood area ratio from 23.9\ub11.2 (May) to 15.2\ub11.5 (July). While A. unedo also underwent an almost stepwise loss on hydraulic conductivity, such a loss did not occur for Q. ilex, whereas P. latifolia was able to slightly increase its hydraulic conducitivity. These differences show how different plant compartments coordinate differently between species in their responses to drought. The different responses appear to be mediated by different root distributions of the species and their relative resistances to drought are likely to depend on the duration of the periods in which water remains extractable in the upper soil layers

Enhancement of co-production of nutritional protein and carotenoids in Dunaliella salina using a two-phase cultivation assisted by nitrogen level and light intensity

Microalga Dunaliella salina is known for its carotenogenesis. At the same time, it can also produce high-quality protein. The optimal conditions for D. salina to co-produce intracellular pools of both compounds, however, are yet unknown. This study investigated a two-phase cultivation strategy to optimize combined high-quality protein and carotenoid production of D. salina. In phase-one, a gradient of nitrogen concentrations was tested. In phase-two, effects of nitrogen pulse and high illumination were tested. Results reveal optimized protein quantity, quality (expressed as essential amino acid index EAAI) and carotenoids content in a two-phase cultivation, where short nitrogen starvation in phase-one was followed by high illumination during phase-two. Adopting this strategy, productivities of protein, EAA and carotenoids reached 22, 7 and 3 mg/L/d, respectively, with an EAAI of 1.1. The quality of this biomass surpasses FAO/WHO standard for human nutrition, and the observed level of β-carotene presents high antioxidant pro-vitamin A activity