Modeling of vegetation dynamics in hydrological models for the assessment of the effects of climate change on evapotranspiration and groundwater recharge

Vegetation affects water balance of the land surface by e.g. storage of precipitation water in the canopy and soil water extraction by transpiration. Therefore, it is essential to consider the role of vegetation in affecting water balance by taking into account the temporal dynamics of e.g. leaf area index, rooting depth and stomatal conductance in hydrological models. However until now, most conceptual hydrological models do not treat vegetation as a dynamic component. This paper presents an analysis of the effects of the application of two different complex vegetation models combined with a hydrological model on the model outputs evapotranspiration and groundwater recharge. Both model combinations were used for the assessment of the effects of climate change on water balance in a mesoscale catchment loctated in the Northeastern German Lowlands. One vegetation model assumes a static vegetation development independent from environmental conditions. The other vegetation model calculates dynamic development of vegetation based on photosynthesis, respiration, allocation, and phenology. The analysis of the results obtained from both model combinations indicated the importance of taking into account vegetation dynamics in hydrological models especially if such models are used for the assessment of the impacts of climate change on water balance components

Einfluss von Steinkorrekturen bodenhydraulischer Kennwerte auf die Simulationsgüte eine numerischen Bodenwasserhaushaltsmodells -Anwendung auf drei Level-II Forstexperimentalflächen mit hohen Skelettgehalten im Bodenprofil

Für die Abschätzung der Einflüsse des Klimawandels auf die Wasserbilanz von Forstökosystemen sind Langzeitanalysen durch die Anwendung numerischer forsthydrologischer Simulationsmodelle unabdingbar. Für die Anwendung derartiger Modelle müssen jedoch die Kennwerte der Bodenwasserretentionsfunktionen und der hydraulische Leitfähigkeitsfunktion bekannt sein. Diese Kennwerte sind jedoch eigentlich nur für den Feinboden gültig. Viele Forststandorte weisen jedoch in ihren Bodenprofilen z.T. sehr hohe Steingehalte auf. Diese Steingehalte beeinflussen Bodenwärmehaushalt, Infiltration, Bodenwasserspeicherung und –flüsse und sollten daher bei Modellrechnungen zum Wasserhaushalt berücksichtigt werden. In der vorgelegten Studie werden einfache Verfahren zur Steinkorrektur bodenhydraulischer Kennwerte für skelettreiche Bodenprofile von 3 ICP Level-II Forststandorten angewendet und der Einfluss dieser Steinkorrekturen auf die Simulationsgüte eines forsthydrologischen numerischen Wasserhaushaltsmodells analysiert. Zur Einschätzung der Simulationsgüte dienten die Vergleiche von an den Level-II Standorten gemessenen mit simulierten Bestandesniederschlägen, Tensionen und Bodenwassergehalten. Die Anwendung der Steinkorrektur führte in den meisten Fällen zu einer Verbesserung der Simulationsgüte

Evaluation of three different regional climate change scenarios for the application of a water balance model in a mesoscale catchment in Northeast Germany

Future climate changes might have some impacts on catchment hydrology. An assessment of such impacts on e.g. ground water recharge is required to derive adaptation strategies for future water resources management. The main objective of our study was an analysis of three different regional climate change scenarios for a catchment with an area of 2415 km² located in the Northeastern German lowlands. These data sets consist of the STAR-scenario with a time period 1951–2055, the WettReg-scenario covering the period 1961–2100 and the grid based REMO-scenario for the time span 1950–2100. All three data sets are based on the SRES scenario A1B of the IPCC. In our analysis, we compared the meteorological data for the control period obtained from the regional climate change scenarios with corresponding data measured at meteorological stations in the catchment. The results of this analysis indicated, that there are high differences between the different regional climate change scenarios regarding the temporal dynamics and the amount of precipitation. In addition, we applied a water balance model using input data obtained from the different climate change scenarios and analyzed the impact of these different input data on the model output groundwater recharge. The results of our study indicated, that these regional climate change scenarios due to the uncertainties in the projections of precipitation show only a limited suitability for hydrologic impact analysis used for the establishment of future concrete water management procedures in their present state

Model inter-comparison on crop rotation effects ? an intermediate report

Data of diverse crop rotations from five locations across Europe were distributed to modelers to investigate the capability of models to handle complex crop rotations and management interactions

Estimation of soil water content and evapotranspiration from irrigated cropland on the North China Plain

For nearly 30 y, cropland on the North China Plain (NCP) has been irrigated primarily by pumping groundwater with no sustainable management strategy. This has caused a continuous decline of the water table. A sustainable groundwater management and irrigation strategy must be established in order to prevent further decline of the water table; to do this, one must quantify soil water content and daily rates of deep percolation and locate evapotranspiration from irrigated cropland. For that purpose, we developed a three-layer soil-water balance (SWB) model based on an approach described by Kendy et al. (2003). In this model, the unsaturated soil zone is divided into three layers: a surface active layer, a middle active soil layer, and a lowest passive soil layer. The middle and the lowest layers dynamically change with the development of crop rooting depth. A simple "tipping bucket" routine and an exponential equation are used to redistribute soil water in the three soil layers. The actual evapotranspiration estimated is partitioned into soil evaporation and crop transpiration using a dual crop coefficient reference approach. At first, the model was calibrated using data obtained from five deficiently irrigated field plots located at an experimental site in the NCP between 1998 and 2003. Then, the model was validated by comparing estimated soil water contents with measured ones at three other plots with nondeficient irrigation. The estimates of actual evapotranspiration were compared with those measured with a large-scale weighing lysimeter (3 m2). The index of agreement (IA) for soil water contents varied between 0.62 and 0.80; the concordance correlation coefficient (CCC) and the root mean square error obtained from the same comparison were 0.34-0.65 and 0.043-0.074 cm3 cm-3, respectively. The rates of 10 d mean evapotranspiration estimated by the model show a good fit to those measured by the large-scale lysimeter; this is indicated by IA = 0.94 and CCC = 0.88. Our results indicate that at the irrigated cropland on the plain, deep soil water-percolation rates are usually <200mm y-1 under nondeficient-irrigation conditions. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA

Multimodality treatment for poorly differentiated neuroendocrine head and neck carcinomas - a single institution experience

Görner M, Brasch F, Hirnle P, et al. Multimodality treatment for poorly differentiated neuroendocrine head and neck carcinomas - a single institution experience. European Journal of Cancer Care. 2013;22(5):648-652