The reclamation of abondend open-cast mines in the region south of Leipzig raises many scientific questions. This research project focus on the simulation of groundwater recharge. The knowledge of the processes of water infiltration is necessary to control the recharge and quality of groundwater. Empirical and mathematical methods will be combined to estimate the groundwater recharge according to substrate, vegetation and landuse. For this purpose on the open-cast mine Espenhain two soil long-term observation stations under different landuse conditions (forest, agricultural area) were installed. The following parameters are measured in different levels up to 2 m depth continuously every 30 minutes: Soil water content, water tension, soil temperature. On the forest station stem flow and precipitation are determined. On the agricultural area open land precipitation, air temperature, air humidity and albedo are registered automatically. Soil water and rainfall are analyzed on heavy metal contents as well as different cations and anions. Parallel to the field measurements on the institute workstation the computer model WASMOD was used for long-term predictions of groundwater recharge. The WASMOD model is calibrated with the measured data of the observation stations and coupled with a geographical information system in order to obtain groundwater recharge for the Espenhain dump.

The reclamation of abondend open-cast mines in the region south of Leipzig raises many scientific questions. This research project focus on the simulation of groundwater recharge. The knowledge of the processes of water infiltration is necessary to control the recharge and quality of groundwater. Empirical and mathematical methods will be combined to estimate the groundwater recharge according to substrate, vegetation and landuse. For this purpose on the open-cast mine Espenhain two soil long-term observation stations under different landuse conditions (forest, agricultural area) were installed. The following parameters are measured in different levels up to 2 m depth continuously every 30 minutes: Soil water content, water tension, soil temperature. On the forest station stem flow and precipitation are determined. On the agricultural area open land precipitation, air temperature, air humidity and albedo are registered automatically. Soil water and rainfall are analyzed on heavy metal contents as well as different cations and anions. Parallel to the field measurements on the institute workstation the computer model WASMOD was used for long-term predictions of groundwater recharge. The WASMOD model is calibrated with the measured data of the observation stations and coupled with a geographical information system in order to obtain groundwater recharge for the Espenhain dump.

Water resources demand and natural disasters related to hydro meteorological events haveincreased the interest in hydrological studies in Panama. Runoff estimations are importantfor effective water resources management in any catchment, but the limited quantity andquality of the available hydrological and meteorological data in Panama make it hard forresearchers to come to conclusive statements that can help in good planning. This issue hasto be addressed, but meanwhile, the challenge is to try to understand the hydrologicalprocesses occurring in any catchment with the available data.The relationship between rainfall and runoff in the Juan Diaz River basin is not wellunderstood and its fast response due to high rainfall intensities in the area is a concern inthe community and authorities. The meteorological and hydrological data in the Juan DiazRiver basin are also limited. The main objective of this thesis was to establish how well theJuan Diaz River basin can be hydrologically represented by records of the availableinstrumentation. This was performed with a hydrological, WASMOD, and a statistical model,linear multiple regression. Both models simulated daily and monthly runoff for a period of 21years. For the long term water balance, a graph showing discharge against rainfall data wasplotted in the yearly scale to establish a relationship between the two variables.Precipitation records from an active meteorological station, which was the closest to thebasin from the ones with available records, were used in this study to estimate the arealmean precipitation of the basin, since nowadays there are no active meteorological stationswithin the basin.It was not possible to represent the Juan Diaz River basin well with the two models in thedaily and monthly resolution. Uncertainties in the precipitation input and in the dischargeoutput data were considered to be the reasons for the poor simulations. That said, it can bestated that the available instrumentation at this point is not sufficient for modeling. In thelong term water balance, the instrumentation can be used for water estimations, but carehas to be taken if this approach is used since the limited quantity of data in this scale werescattered around the predictions.Efforts have to be made to encourage decision makers to increase the availableinstrumentation in the Juan Diaz River basin, in order to make accurate simulations orforecasting that will better support water resources management. / La demanda de recursos hídricos y la ocurrencia de desastres naturales relacionados con eventoshidro‐meteorologicos han incrementado el interés de estudios hidrológicos en Panamá.Estimaciones de escorrentía son importantes para el manejo efectivo de los recursos hídricos encualquier cuenca, pero la calidad y cantidad limitada de registros hidrológicos y meteorológicosen Panamá hacen difícil a los investigadores llegar a conclusiones contundentes que puedanayudar a una buena planificación. Este problema debe ser abordado, pero entretanto, el reto estratar de entender los procesos hidrológicos que ocurren en las cuencas con los registrosdisponibles.La relación lluvia‐escorrentía en la cuenca del Río Juan Díaz no se entiende completamente y surápida respuesta debido a las lluvias de alta intensidad en el área es una preocupación en lacomunidad y en las autoridades. Los registros meteorológicos e hidrológicos en la cuenca del RíoJuan Díaz son limitados. El objetivo principal de esta tesis fue establecer que tan bien se podíarepresentar hidrológicamente la cuenca del Río Juan Díaz con los registros disponibles de lainstrumentación existente hoy en día en la misma. Esto se realizo con un modelo hidrológico,WASMOD, y con un modelo estadístico, regresión lineal múltiple. Ambos modelos simularonescorrentía diaria y mensual por un período de 21 años. Para el balance hídrico a largo plazo, segraficaron en la escala anual los datos de caudal contra los datos de precipitación paraestablecer una relación entre ambas variables.Registros de precipitación de una estación meteorológica activa, la cual era la más próxima a lacuenca de las estaciones con registros disponibles, fueron utilizados en este estudio para estimarla precipitación promedio areal de la cuenca, dado que hoy en día no hay ninguna estaciónmeteorológica activa dentro de la misma. En la escala diaria y mensual, no fue posiblerepresentar bien la cuenca del Río Juan Díaz con los dos métodos seleccionados. Incertidumbresen los datos de entrada y salida fueron consideradas las razones de las pobres simulaciones.Dicho lo anterior, se puede concluir que la instrumentación existente en la cuenca hoy en día noes suficiente para su modelación hidrológica. En el balance hídrico a largo plazo, lainstrumentación existente podría usarse pero cuidado debe tenerse si esta aproximación esutilizada ya que la cantidad limitada de datos en esta escala estaba dispersa alrededor de laspredicciones.Esfuerzos tienen que hacerse para alentar a los tomadores de decisiones en Panamá paraaumentar la instrumentación existente en la cuenca del Río Juan Díaz, para así poder hacer lamisma posible para predicciones que servirán para una mejor planificación de sus recursos.

Water has always had a controlling influence on the earth’s evolution. Understanding and modelling the large-scale hydrological cycle is important for climate prediction and water-resources studies. In recent years large-scale hydrological models, including the WASMOD-­M evaluated in the thesis, have increasingly become a main assessment tool for global water resources. The monthly version of WASMOD-M, the starting point of the thesis, revealed restraints imposed by limited hydrological and climate data quality and the need to reduce model-structure uncertainties. The model simulated the global water balance with a small volume error but was less successful in capturing the dynamics. In the last years, global high-quality, high-resolution topographies and hydro­graphies have become available. The main thrust of the thesis was the development of a daily WASMOD-M making use of these data to better capture the global water dynamics and to parameter­ise local non-linear processes into the large-scale model. Scale independency, parsimonious model structure, and computational efficiency were main concerns throughout the model development. A new scale-independent routing algorithm, named NRF for network-response function, using two aggregated high-resolution hydrographies, HYDRO1k and HydroSHEDS, was developed and tested in three river basins with different climates in China and North America. The algorithm preserves the spatially distributed time-delay information in the form of simple network-response functions for any low-resolution grid cell in a large-scale hydrological model. A distributed runoff-generation algorithm, named TRG for topography-derived runoff generation, was developed to represent the highly non-linear process at large scales. The algorithm, when inserted into the daily WASMOD-M and tested in same three basins, led to the same or a slightly improved performance compared to a one-layer VIC model, with one parameter less to be calibrated. The TRG algorithm also offered a more realistic spatial pattern for runoff generation. The thesis identified significant improvements in model performance when 1) local instead of global climate data were used, and 2) when the scale-independent NRF routing algorithm was used instead of a traditional storage-based routing algorithm. In the same time, spatial resolution of climate input and choice of high-resolution hydrography have secondary effects on model performance. Two high-resolution topographies and hydrographies were used and compared, and new tech­niques were developed to aggregate their information for use at large scales. The advantages and numerical efficiency of feeding high-resolution information into low-resolution global models were highlighted. / Vatten har alltid varit en nyckelfaktor för jordens utveckling. Att förstå och kunna modellera det storska­liga vattenkretsloppet är betydelsefullt såväl för klimatförutsägelser som för studier av vattenresur­ser. På senare år har storskaliga hydrologiska modeller, däribland WASMOD-M som utvärderas i denna avhand­ling, i ökande utsträckning kommit att användas som huvudverktyg för utvärdering av globala vattenresurser. Den månatliga versionen av WASMOD-M, avhandlingens startpunkt, användes för att påvisa inskränk­ningar som låg i begränsande hydrologi- och klimatdata liksom behovet av att minska model­lens strukturella osäkerheter. Modellen simulerade den globala vattenbalansen med ett mycket litet volymfel (avrinningens långtidsmedelvärde) men var mindre lyckosam att efterlikna dynamiken. Under se­nare tid har globala topografiska och hydrografiska data med hög rumslig upplösning och kvalitet blivit tillgängliga. Avhandlingens huvudsakliga drivkraft var att utveckla WASMOD-M med hjälp av dessa data i syfte att bättre fånga den globala vattendynamiken och för att parametrisera lokala ickelin­jära processer i den storskaliga modellen. Under hela modellutvecklingen har skaloberoende, lågparametrise­rad modellstruktur och numerisk beräkningseffektivitet varit viktiga bivillkor. En ny skaloberoende svarstidsalgoritm, benämnd NRF (network-response function), som utnyttjar två aggregerade högupplösta hydrografier, HYDRO1k och HydroSHEDS, utvecklades och provades i tre avrinningsområden med olika klimat i Kina och Nordamerika. Algoritmen bevarar den rumsligt fördelade informationen om koncentrationstider i form av enkla responsfunktioner för vattendragsnä­tet för godtyckliga lågupplösta beräkningsrutor in en storskalig hydrologisk modell. En distribuerad algoritm för avrinningsbildning, benämnd TRG (topography-derived runoff genera­tion), utvecklades för att representera den höggradigt ickelinjära processen i större skalor. Algoritmen användes i den dagliga WASMOD-M och provades i samma tre avrinningsområden som ovan. Modellprestanda blev lika bra eller bättre än en enlagers VIC-modell fast med en parameter mindre att kalibrera. TRG-algoritmen gav ett rimligare rumsligt mönster för avrinningsbildningen. Avhandlingen har identifierat påtagliga förbättringar i modellprestanda när 1) lokala i stället för globala klimatdata användes och 2) när NRF, den skaloberoende svarstidsalgoritmen användes i stället för en traditionell magasinsbaserad svarstidsalgoritm. Samtidigt har klimatdatas rumsliga upplösning och val av högupplöst hydrografi en andra ordningens inverkan på modellprestanda. Två högupplösta topografier och hydrografier användes och jämfördes, och nya tekniker utveckla­des för att aggregera deras informationsinnehåll i stora skalor. Fördelarna och den numeriska beräkningsef­fektiviteten av högupplöst information i lågupplösta globala modeller har belysts.