In this study, semi-distributed hydrological model studies were carried out with the Mike11 model in Yuvacik dam Basin. The basin with a drainage area of 257.8 km2 is located in 12 km South East of Izmit city in T&uuml / rkiye. The basin is divided into three sub-basins named as Kirazdere, Kazandere and Serindere where each sub-basin is represented by its own characteristics. The largest peaks of inflow were observed when the storm events occur due to both snowmelt and rain. Therefore, observed flows for the period of 2001-2006 were grouped as daily and hourly storm events according to the event types such as rainfall, snowmelt or mixed events. Rainfall- Runoff Model (NAM) module of the model was used for the simulation of daily snowmelt and rain on snow events and Unit Hydrograph Method (UHM) module was used for the simulation of hourly rainfall events. A new methodology is suggested for the determination of Curve Number (CN) of the sub-basins by using the fractional area and topographic index values combined with hourly model simulations. The resulting CN values were used in the UHM module v and the suggested CN approach has been validated with the classical SCS-CN approach with GIS analysis. As a result of the study, the parameters of each sub-basin are calibrated with hourly and daily model simulations. The resulting flows are compared with the observed flows where model efficiency is tested with visual and statistical evaluations. The modeling studies give promising results for the computation of runoff during different seasons of a year.

Environmental concerns are becoming increasingly relevant during a period of hemorrhaging ecosystem goods and services. Restoring these would result in positive outcomes for public health and economic benefit. This thesis seeks to address two environmental concerns: (1) accurate soil mapping and (2) treatment of nitrogen to affect water quality change.The current method of soil mapping, SSURGO (USDA‐NRCS Soil survey), is often erroneous and misleading. Two studies in this dissertation are conducted to evaluate the potential that different resolution digital elevation models (DEMs) have to distribute soil characteristics successfully. These studies are conducted in southwest Virginia and western Vermont. The aforementioned studies evaluated 36 and 59 soil samples, respectively. Spatial characteristics, including slope, catchment area, and topographic wetness, are derived from several DEMs. In chapter 2, these characteristics are spatially compared, and we found that small resolution rasters result in narrow flow paths relative to coarser rasters. In chapter 3, we isolate the analysis to focus on resolution size, instead of a mix of both resolution size and generation method. This is done by recursively coarsening small rasters, deriving spatial attributes from said rasters and evaluating their potential to fit the soil characteristics of interest. Here we found that slopes generated from resolutions smaller than 11m were poor predictors of soil characteristics. Both chapters are finished by proposing and evaluating a soil map. Proposed regressions beat SSURGO in all investigated properties. Furthermore, proposed maps consistently beat out uninformed smallest resolution derived maps.Chesapeake bay water quality managers are struggling to achieve targets for nitrogen loading. This is in part due to the widespread presence of legacy nitrogen. Legacy nitrogen is an emerging issue, and springs exporting high levels of nitrogen are not uncommon in northern Virginia. This thesis explores, in part, a novel concept of treating large loads of nitrogen exported from a spring with a bioreactor. Bioreactors are a young science that most typically pair carbon heavy subterranean receptacles to agricultural drainage. This provides a location for nitrogen fixing bacteria to consume nitrate/nitrite, turning these into inert nitrogen gas. A spring fed bioreactor is studied for 10 months, and bioreactor conditions including influent and effluent nitrogen concentrations, bioreactor flow, and temperature are collected. A model driven by first order reaction equations is found to be most accurate with inputs of temperature and bioreactor age. The resulting marginal effects of these inputs were consistent with previously reported studies. / Doctor of Philosophy / Centuries of industrialization have resulted in widespread human progress but have, at times, adversely impacted the environment. Constituents rely heavily on environmental services, such as clean air and water, to subsist. Environmental degradation has resulted in detrimental effects to public health, and remediation is currently economically viable. As such, there are strong incentives for researchers to understand environmental processes at a fundamental level. One such process is soil characteristic distribution. The distribution of soil characteristics, such as soil texture or organic matter, is especially important for agriculturalists, hydrologists and geotechnicians. Soil texture and organic matter distribution can affect crop yield, nitrogen export to surface waters, and structural stability of soils. Thus, accurate characterization of measured soil properties is paramount to multiple fields. The most typically used soil map is USDA‐NRCS Soil survey (commonly referred to as SSURGO). Currently, the SSURGO database is a poor predictor of soil characteristics. There is an opportunity to improve soil characteristic distribution using digital elevation models (DEMs). As DEMs become cheaper to develop, they are typically available in multiple resolutions and generation methods. In this research, several DEMs are used to better soil maps for watersheds in Southwest Virginia and Western Vermont. Both studies showed that DEMs can better distribute soils when compared to the current SSURGO maps. Additionally, we showed that the finest resolution dataset was not always best, and mixed resolution topographic wetness indices to be most advantageous for distributing soils.Another such process is remediation of surface waters from high loads of nitrogen and phosphorus. The Haber-Bosch method of producing nitrogen fertilizer is one of the most important human innovations in recent history. This method is likely responsible for the aversion of widespread famine in the early 1900s. However, residents of multiple river systems, including the Chesapeake Bay and the Mississippi River, are suffering from the adverse effects of widespread hypoxic/anoxic (with little/no oxygen, respectively) zones within water. These have partially been responsible for the decline of commercial ventures such as fisheries and tourism. These zones are caused by eutrophication, a process of unsustainable plant growth in the presence of nitrogen and phosphorus. Water quality managers typically target agricultural runoff and point source polluters when trying to eliminate anthropogenic nitrogen. However, legacy nitrogen (nitrogen stored in groundwater in excess of a year) has become an emerging concern for water quality. It is not uncommon for springs in karst areas to be contaminated with high concentrations of nitrogen. These springs present a point source that can be treated by an emerging technology: bioreactors. Bioreactors are subterranean, woodchip filled basins that provide a location for microbes to exchange water soluble nitrogen for inert nitrogen gas. The consistency in nitrogen loading and constant flow provide stability relative to more traditional bioreactor installations. Most typically, bioreactors are installed downstream of agricultural drainage systems, and influent flow and nitrogen load depend wholly on precipitation/irrigation and nitrogen application. In this thesis, a novel spring fed bioreactor is studied. Removal rates of nitrogen are quantified using a regression driven by reaction kinetics. The analysis showed bioreactor efficiency was intimately related to hydraulic residence time, nitrogen loading, bioreactor bed temperature, and bioreactor age. The spring fed bioreactor is found to be advantageous because of its consistency, and disadvantages because springs are colder and thus less efficient than typical irrigated runoff.

<p>The main objectives of this work were to investigate Geographical Information Systems techniques for modelling a cross-country trafficability. To accomplished stated tasks, reciprocal relationships between the soil deposits, local hydrology, geology and geomorphology were studied in relation to the study area in South-Eastern Sweden.</p><p>Growing awareness of nowadays users of GIS in general is being concentrated on understanding an importance of soil conditions changed after cross-country trafficability. Therefore, in this thesis, constructing of the Soil Knowledge Database introduced to the genuine geological soil textural classes a new, modified geotechnical division with desirable for off-road ground reasoning measurable factors, like soil permeability, capillarity or Atterberg’s consistency limits.</p><p>Digital Elevation Model, the driving force for landscape studies in the thesis, was carefully examined together with the complementary datasets of the investigated area. Testing of the elevation data was done in association to the hydrological modelling, which resulted with the Wetness Index map. The three distinguishable soil wetness conditions: dry, moist and wet, were obtained, and used consequently for creation of the static ground conditions map, a visible medium of soils susceptibility to for example machine compaction.</p><p>The work resulted with a conceptual scheme for cross-country trafficability modelling, which was put into effect while modeling in GIS. As a final outcome, by combining all processed data together, derivatives were incorporated and draped over the rendered 3D animating scene. A visually aided simulation enabled to concretized theoretical, hypothetical and experimental outcomes into one coherent model of apprised under Multicriterial Evaluation techniques standardized factor maps for ground vehicle maneuverability. Also further steps of research were proposed.</p>

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.

The main objectives of this work were to investigate Geographical Information Systems techniques for modelling a cross-country trafficability. To accomplished stated tasks, reciprocal relationships between the soil deposits, local hydrology, geology and geomorphology were studied in relation to the study area in South-Eastern Sweden. Growing awareness of nowadays users of GIS in general is being concentrated on understanding an importance of soil conditions changed after cross-country trafficability. Therefore, in this thesis, constructing of the Soil Knowledge Database introduced to the genuine geological soil textural classes a new, modified geotechnical division with desirable for off-road ground reasoning measurable factors, like soil permeability, capillarity or Atterberg’s consistency limits. Digital Elevation Model, the driving force for landscape studies in the thesis, was carefully examined together with the complementary datasets of the investigated area. Testing of the elevation data was done in association to the hydrological modelling, which resulted with the Wetness Index map. The three distinguishable soil wetness conditions: dry, moist and wet, were obtained, and used consequently for creation of the static ground conditions map, a visible medium of soils susceptibility to for example machine compaction. The work resulted with a conceptual scheme for cross-country trafficability modelling, which was put into effect while modeling in GIS. As a final outcome, by combining all processed data together, derivatives were incorporated and draped over the rendered 3D animating scene. A visually aided simulation enabled to concretized theoretical, hypothetical and experimental outcomes into one coherent model of apprised under Multicriterial Evaluation techniques standardized factor maps for ground vehicle maneuverability. Also further steps of research were proposed.