The coupling and integration of models from different disciplines to an interdisciplinary modeling network facilitates the simultaneous description of effects due to ecological, economical or legal changes of land management in selected areas of the natural environment. In all these models soils play a crucial role with their physical and chemical characteristics. In the Interdisciplinary Research Project ”︁Land use concepts for peripheral regions” (Sonderforschungsbereich SFB 299) three mesoscale GIS‐based models are developed and adapted to specific conditions of a low German mountain range: the comparative static economic model ProLand, the habitat models ANIMO, ELLA, and YELL, and the hydrological continuum model SWAT. As an example of the interdisciplinary model network, it is demonstrated how changes in land management due to increasing field size affect the landscape services natural production, economic output, water balance, and biodiversity. Numerous soil parameters are employed simultaneously in a variety of modules and processes in these models. The economic model ProLand requires soil data to assess tillage costs, the potential yield from agriculture and forestry production. In order to regionalize the occurrence of typical species by ANIMO and ELLA, universal soil descriptions in combination with exposure classes are formulated and delineated by GIS on the basis of a soil map at 1:50,000 and a digital elevation model. Especially soil physical properties are input parameter of high sensitivity for the hydrological model SWAT. Whenever soil parameters are to be used in interdisciplinary modeling approaches great care must be devoted whether the preconditions for such an application are fulfilled. This problem is pointed out by some examples.

Water pollution by nitrogen originates at diffuse and point sources. In surface aquatic systems, nitrate is one of the most problematic forms of nitrogen, causing phytoplankton and macrophyte growth and consequently water eutrophication. This study evaluated whether the Soil and Water Assessment Tool (SWAT) model can simulate nitrate load in a rural watershed in daily and monthly time increments. The study investigated 462 km² of the upper part of the Stör catchment, a typical rural lowland catchment located in Northern Germany. The results showed that simulations of nitrate load at monthly increments are better predictors of observed data than daily simulations. The most effective practices to minimize the NO3-N load were the reduction of nitrogen fertilizer application and the increasing of conservation areas, such as field filter strips.Keywords: land use, nitrogen pollution, non-point pollution, SWAT model. Melhores práticas de manejo para reduzir a poluição por nitrato em uma bacia hidrográfica rural na Alemanha RESUMOA poluição da água causada por nitrogênio é originada por fontes difusas e pontuais. Em sistemas aquáticos superficiais, o nitrato é uma das formas mais problemáticas de nitrogênio, causando crescimento de fitoplâncton e de macrófitas e consequentemente a eutrofização da água. Este estudo teve o objetivo de avaliar se o modelo Soil and Water Assessment Tool (SWAT) pode simular a carga de nitrato em uma bacia hidrográfica rural em séries diárias e mensais. Foram investigados 462 km² da parte superior da bacia hidrográfica do rio Stör, uma bacia de planície tipicamente rural localizada no norte da Alemanha. Os resultados mostraram que as simulações de carga de nitratos em incrementos mensais são melhores preditores de dados observados do que simulações diárias. As práticas mais efetivas para minimizar as cargas de NO3-N foram a redução da aplicação de fertilizante nitrogenado e o incremento de áreas de conservação, tal como as faixas filtro.Palavras-chave: nitrogênio, polluição difusa, modelo SWAT, uso da terra. 889Best management practices to reduce nitrate pollution ...Rev. Ambient. Água vol. 12 n. 6 Taubaté -Nov. / Dec. 2017

With increased interest and requirements in surface water quality and hydrodynamics, additional information is needed about water flow in streams. The mobile OTT Qliner with acoustic Doppler technology (ADQ) provides a highly efficient and accurate way of collecting this information. For this study we completed 366 measurements of flow velocity, water depth and discharge with ADQ from September 2010 to June 2011 at 174 cross-sections in eight catchments of different sizes located in northern Germany, central Germany and southeastern China. The measurements were used to study the accuracy, reproducibility and sensitivity of the device, and to improve the hydrodynamic sampling for medium-sized rivers and channels by investigating its internal settings. The observations reported clearly show that the results of flow average, profile, layer and point values obtained with the ADQ compare very well with those of electromagnetic or ultrasonic devices. In general, the average flow velocity gives the highest agreement. Vertical velocity has a better quality than the layer velocity, which indicates a greater precision in the horizontal than in the perpendicular direction. Point velocity, the composite of vertical velocity and layer velocity, has intermediate precision. Tests on internal settings revealed that measurement is more sensitive to cell size than to time interval setting. A cell size to depth ratio of between 0.1 and 0.2 m produced the highest reliability. A measurement period of 30 s is needed for velocities faster than 0.3 m/s; for shallow and slow-flowing rivers, an interval of 50 s or even greater is recommended. The closer the measured points were to the river bank or bed, the greater the measurement error. The river bed can also influence the measurement more distinctly than the river bank. Les observations rapportées montrent clairement que les résultats de valeurs moyennes, le long d'un profil, à une profondeur donnée ou en un point, obtenus avec la TDA se comparent très bien avec ceux des dispositifs électromagnétiques ou à ultrasons. En général, le meilleur accord est obtenu pour la vitesse moyenne. La vitesse selon un profil est de meilleure qualité que la vitesse à une profondeur donnée, ce qui indique une plus grande précision dans le sens horizontal que dans la direction perpendiculaire. La vitesse ponctuelle, procédant de la vitesse selon un profil et selon une profondeur, a une précision intermédiaire. Des essais de réglage internes ont révélé que la mesure est plus sensible à la taille des cellules qu'au réglage de l'intervalle de temps. Un rapport entre la taille de cellule et la profondeur compris entre 0,1 et 0,2 m a fourni les résultats les plus fiables. Une période de mesure de 30 s est nécessaire pour des

Algal blooms have caused severe problems in Lake Taihu, China. Early warning of phytoplankton accumulation can support decision-making against harmful algal bloom events. To investigate the performance of different models in forecasting high phytoplankton biomass, we developed a mechanistic, a regression and three artificial neural network (ANN) models to predict shortterm (3 days) changes of phytoplankton biomass (expressed as chlorophyll-a concentration) in Gonghu Bay of Lake Taihu. We determined the input variables of the ANN models with a sensitivity analysis, and optimized their parameters with a trial-and-error approach. The sensitivity analysis revealed the effects of the input variables on phytoplankton biomass. To calibrate and validate the models, we collected two data sets of Lake Taihu in 2009: hourly-averaged data collected by an automatic monitoring system and field data with a sampling interval of twice a week. Although the sensitivity analysis results vary among the five models, there is a general consensus that phytoplankton changes are significantly affected by water temperature in Gonghu Bay. The ANN models obtained good model fit indicating their practical values in predicting non-linear phytoplankton dynamics for water management purpose. The mechanistic model predicted the phytoplankton distribution dynamically and described the variable interactions explicitly. The regression model is characterized by its easy development. This comparison study assists the modelers in selecting an approximate model for their specific purposes.

Summary Length‐weight relationships (LWRs) were estimated for two fish species from the Jialing River in southwestern China. Specimens were landed seasonally from January 2014 to December 2015 at three locations in the Jialing River and four times fishing activities were occurred in each season at each location. Fishing gear used for sampling included 2, 5, 8 and 10 cm mesh gill nets (50 m long × 1.5 m high). This study presents the LWRs for two species of Culter oxycephaloides Kreyenberg & Pappenheim, 1908 and Gnathopogon herzensteini (Günther, 1896). The LWRs were estimated using the equation W = aLb. The b values were 2.6513 and 3.2245 for C. oxycephaloides and G. herzensteini respectively. The constant values of a were determined as 0.0330 for C. oxycephaloides and 0.0111 for G. herzensteini. This result provides primary data for future fish research and conservation regarding these species in the Jialing River.