Tese(doutorado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2012. / Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2013-12-15T10:09:04Z No. of bitstreams: 1 karina.pdf: 8139075 bytes, checksum: c30bac487b6f4defadafc03c71b60d50 (MD5) / Approved for entry into archive by Sabrina Andrade (sabrinabeatriz@ibest.com.br) on 2013-12-18T17:52:30Z (GMT) No. of bitstreams: 1 karina.pdf: 8139075 bytes, checksum: c30bac487b6f4defadafc03c71b60d50 (MD5) / Made available in DSpace on 2013-12-18T17:52:30Z (GMT). No. of bitstreams: 1 karina.pdf: 8139075 bytes, checksum: c30bac487b6f4defadafc03c71b60d50 (MD5) Previous issue date: 2012 / A alta produtividade na zona costeira e na Plataforma Continental do Sul do Brasil é dada pelo aporte de nutrientes, os quais são determinantes para a produção primária. As regiões de plataforma (Santa Marta-SC 28,60ºS e Albardão-RS 33,20ºS) foram selecionadas por apresentarem características diferenciadas em relação à topografia, sazonalidade e dinâmica das massas de água. Sendo assim, essas possuem diferentes mecanismos de fertilização, além dos aportes continentais. A proximidade à zona de Convergência Subtropical (CST) é determinante para a produtividade dessas regiões, visto que: no inverno, a intrusão da Água Subantártica de Plataforma na região do Albardão aumenta consideravelmente as concentrações de nutrientes na região e; no verão, a Água Central do Atlântico Sul resultado da CST aflora na região de Santa Marta, sendo responsável por 60% da produção nova local. Além disso, aportes subterrâneos foram evidenciados tanto na zona costeira quanto na região de plataforma. No extremo sul do Brasil verificou-se, mediante a variação espaço-temporal de isótopos naturais de rádio e radônio, a ocorrência de advecção de água subterrânea ao longo de toda a costa, desde a desembocadura da Lagoa dos Patos até as proximidades do Uruguai (média: 2,17± 0,2 cm d-1). Com a aplicação de modelos pré-estabelecidos, foi possível calcular os fluxosde nutrientes para a zona costeira (NIT: 21 105 mol d-1) e avaliar o potencial produtivo relacionado a essas descargas (2800 gC m-2 ano-1). Desse modo, entende-se que a parcela de água subterrânea deva ser definitivamente incluída no balanço de massas da região, uma vez que apresenta um potencial produtivo de 7 a 32 vezes maior quando comparado às outras regiões onde a estimativa foi realizada. / High productivity on the coastal region and on the Southern Brazil Continental Shelf is provided by the nutrient input which is fundamental to primary productivity. The regions of Santa Marta, SC (28.60ºS) and Albardão, RS (33.20ºS) were selected due to their special characteristics regarding the topography, seasonality and dynamics of their water mass. Therefore, these areas have different fertilization mechanisms besides the continental input. The proximity to the subtropical convergence zone (SCZ) is determinant in relation to productivity because, in winter, the intrusion of the Subantarctic Shelf Water (SSW) in the Albardão region considerably increases the nutrient concentration whereas, in summer, the South Atlantic Central Water (SACW) that results from the SCZ, moves to the Santa Marta region and is responsible for 60% of the new local production. In addition, subterraneous input was observed both on the coastal areas and on the shelf. In southern Brazil, spatial - time variations of radionuclides (Ra e Rn) show the occurrence of groundwater advection along the coast, from the mouth of Patos Lagoon to Uruguay rates (average: 2.17± 0.2 cm d - 1). Using mathematical models, it was possible to calculate the discharge of nutrients on the coastal zone (TIN: 21105 mol d - 1) and evaluate the productive potential regarding the Submarine Groundwater Discharge (2800 gC m - 2 y - 1). Thus, this study suggests that the portion of ground water should definitely be included in the mass budget of the region, since its productive potential is 7 to 32 times higher by comparison with other regions where this estimate was also carried out.

This thesis aimed to evaluate the groundwater discharge distribution in the Krycklan catchment by developing a groundwater flow model using COMSOL Multiphysics and assuming a topography- controlled groundwater surface. Previous research has shown that the groundwater surface can be modeled as a subdued replica of the topography in humid climate regions where the permeability of the subsurface is low and where the groundwater surface is shallow. In earlier studies by Mojarrad (2021), it has been shown that the modeled infiltration becomes higher than the observed infiltration when a topography-controlled groundwater surface boundary is used and that a solution to this is to decrease the resolution in recharge areas. This method was therefore used in the thesis; however, the modeled infiltration was unsuccessfully lowered. This is thought to be due to differences between the model and the previous study and which are discussed further in this thesis. The discharge and recharge areas were identified using the direction of the vertical component of Darcy velocity, and the discharge flow distribution was evaluated in ArcMAP. The discharge flow distribution in the landscape was compared to real geographical data of surface water to identify a discharge threshold value for when the water balance is upheld by surface water flow or by evapotranspiration. The evapotranspiration discharge flow distribution was also evaluated, where the highest flow values were found in riparian zones of the landscape. / Syftet med denna avhandling var att utvärdera föredelningen av grundvattnets utflöde i Krycklans avrinningsområde genom att utveckla en grundvattenflödesmodell i COMSOL Multiphysics med antagandet av en topografikontrollerad grundvattenyta. Tidigare forskning har visat att grundvattenytan kan modelleras som en dämpad kopia av topografin i fuktiga klimatområden där permeabiliteten i underytan är låg och där grundvattenytan är grund. En implikation av att använda en topografikontrollerad grundvattenyta har visat sig vara att den modellerade infiltrationen blir högre jämfört med den observerade infiltrationen. Tidigare studier av Krycklans avrinningsområde har visat att genom att minska upplösningen i infiltrationsområden kan den modellerade infiltrationen framgångsrikt sänkas, därför användes denna mesh-utjämningsmetod i avhandlingen. För validering av modellen jämfördes den modellerade infiltrationen med den observerade infiltrationen i Krycklans avrinningsområde. Valideringen visade att mesh-utjämningen misslyckades med att minska infiltrationen, vilket tros bero på skillnader mellan modellen och den tidigare studien och som diskuteras vidare i denna avhandling. Grundvattnets infiltration- och utflödesområden identifierades med hjälp av riktningen på den vertikala komponenten av Darcy-hastighet, och utflödesfördelningen utvärderades i ArcMAP. Utflödesfördelningen i landskapet jämfördes med verkliga geografiska data för ytvatten för att identifiera ett tröskelvärde för utflödet när vattenbalansen upprätthålls av ytvattenflöde eller av evapotranspiration. Fördelningen av utflöden genom evapotranspirations utvärderades också, där de högsta flödesvärdena återfanns i områden nära ytvattenkroppar i landskapet.

Die Arbeit besteht aus mehreren Studien zur Quantifizierung des Grundwasserstroms in Seen (Exfiltration; engl.: lacustrine groundwater discharge, LGD) und damit verbundener Nährstoffeinträge. In zwei einleitenden Kapiteln dieser Arbeit werden eine Gründe für die Vernachlässigung der Grundwasserexfiltration (LGD) in Seen und der daran gekoppelten Nährstoffeinträge identifiziert. Diese Literaturstudien fassen den aktuellen Kenntnisstand zum Einfluss des Grundwassers auf die Hydrologie von Seen und ihre Nährstoffhaushalte zusammen. Den Kern der vorliegenden Arbeit bilden zwei empirische Studien, die sich mit der Quantifizierung der grundwasserbürtigen Phosphor (P)-Fracht in den Arendsee in Deutschland befassen. Das Gesamtvolumen des Grundwasserzustroms wird basierend auf der Grundwasserneubildung im Einzugsgebiet des Sees ermittelt. Lokale Muster der Grundwasserexfiltration werden anhand von Temperaturtiefenprofilen des Seesediments bestimmt. Eine Kombination der Ergebnisse ermöglicht es, die quantitativen Daten mit lokalen Informationen zu unterstützen. Die Untersuchung der Grundwasserqualität zeigt, dass die P-Konzentrationen im Grundwasser im besiedelten Bereich teilweise stark erhöht sind. Als Konsequenz daraus haben die grundwasserbürtigen P-Frachten einen Anteil von mehr als 50% an der gesamten externen P-Last des Arendsees. Das Grundwasser ist damit eine maßgebliche Ursache für die Eutrophierung des Gewässers. Drei weitere Studien widmen sich der Entwicklung und Optimierung von Ansätzen zur qualitativen und quantitativen Bestimmung der Grundwasserexfiltration in Seen. Die kritische Auseinandersetzung mit den Ergebnissen der Studien zeigt die Notwendigkeit weiterer Forschung zur Verbesserung und Standardisierung der Methoden zur Bestimmung von LGD und damit verbundenen Stofftransporten auf. Der Fall des Arendsees sollte alle, Wissenschaftler und Praktiker, dazu motivieren, das Grundwasser als relevante Eutrophierungsquelle in Betracht zu ziehen. / The present work is a collection of studies on lacustrine groundwater discharge (LGD) and groundwater-borne phosphorus (P) loads. For a number of reasons, groundwater exfiltration (i.e., LGD) is often not considered in water and nutrient budgets of lakes. This is also and especially true for P which was often regarded to be immobile in groundwater until recently. Two chapters review the scientific literature regarding the impacts of groundwater on hydrology and nutrient budgets of lakes, respectively. They present mechanisms and processes of LGD as well as techniques and methods to measure LGD and related nutrient transports. Moreover, numbers of LGD volumes and loads reported in literature are presented. The core of the present work is represented by two case studies dealing with the quantification of P loads from LGD to a lake in Germany. A combination of different methods is applied to overcome the problem of quantitative large scale LGD determination without losing local spatial information. P concentrations in groundwater and LGD are investigated by detailed spatial water sampling. The results reveal that P is actually present in concentrations far above natural background concentrations in the urban groundwater. LGD-derived P loads account for more than 50% of the overall external P loads to the lake and by that contribute significantly to lake eutrophication. Three further studies are devoted to the development and improvement of approaches to determine LGD. Critical reviews of the above mentioned studies reveal the need for further research in order to standardize and improve methods for LGD and mass load determination. It is found that the appropriate method for LGD determination depends on the spatial scale of interest. The identification of P introduced by LGD as a main driver of lake eutrophication is an important finding which should encourage scientists, policy makers, and lake managers to consider groundwater as a relevant P source for lakes.