Tap water supply is an essential resource for human societies. However with increasing water use and global warming, this resource needs to be monitored and managed sustainably. Here we use stable isotopes to identify potential issues associated with tap water resources in Canada. We analyze isotopes of 576 tap water samples collected from across Canada and classified them based on their supply sources including groundwater (TapGroundwater), river (TapRiver) and lake (TapLake). We found, isotopic values in tap water correlate strongly with those predicted in local precipitation across Canada, suggesting precipitation is the parent source of tap water. However, this correlation is stronger for TapGroundwater and TapRiver than TapLake. To explain this difference, we constructed a series of water balance models to predict isotopic values of surface water across Canada validated against Canadian rivers isotopes data. We then compared the tap water isotopic values to those predicted in local surface water, which improved the predictability of TapRiver and TapLake but not TapGroundwater. We suggest, TapGroundwater usually reflects isotopic values of annually averaged precipitation whereas TapRiver and TapLake reflect post-precipitation processes. We used the residuals between our observed and predicted isotope data to assess regional sources and processes influencing tap water isotopes across Canada. Regionally, snow/glacier melt from the Rockies contributes to groundwater recharge across Western Canada as well as to some rivers and lakes in Alberta and British Columbia. Also, tap water are highly evaporated across Western Canada irrespective of their sources. Across the Great Lakes and East Coast regions, lakes undergo high evaporative losses. Also, many localities in the East Coast pump and store groundwater in small lakes or ponds exposing them to evaporation. Our data and models provide a baseline for isotope monitoring of tap water resources and isotope forensic studies across Canada.

This thesis aims to analyze the water issue in the Sergipe basin of Vaza Barris river. To this end, the social environmental approach was taken as a methodological assumption, since the water problem is a reflection of the relations established by the interaction between society and nature. Thus, this study included a survey of geo-environmental issues involving land use and the uses of water resources and the livelihood of its inhabitants. We also analyzed the public policies related to this issue, identifying the role that social actors play about water management, concluding with a local water management proposal. To this end, documentary, bibliographic and field surveys were done and they have been prepared on thematic maps of geo-environmental conditions, as well as the socioeconomic characteristics of the basin by means of exploratory data analysis side, both associated with field activities. Occupying an area of 2559.0 km², the basin covers 14 municipalities, nine of which have their headquarters in this city included spatial area. Climatic, hydrological and soil aspects determine water limitations in the upper and middle-down strokes. In relation to land use activities, they are mostly focused on the primary sector. In demographic terms, it has a total population of around 280,000 inhabitants, and the occupation of their space has been happened in a disorderly manner. One of the consequences of this factor can be found in the precariousness of the infrastructure of basic sanitation, the degradation of surface waters and high socioenvironmental and water vulnerability. Nevertheless, besides having been found that most of the local population has low incomes, combined with a low education level, public policies aimed at the rational use of water resources in this basin are still incipient, also being explicit the absence water management. Finally, it was found that the unit of federal river basin presents limitations for effective water management in Sergipe Vaza Barris water, because the analysis of geo-environmental conditions and living conditions in that area expresses the need for management, especially at the local level. / Esta tese tem como objetivo analisar a questão hídrica na bacia sergipana do rio Vaza Barris. Para tal, a abordagem socioambiental foi tomada como pressuposto metodológico, posto que a problemática hídrica é o reflexo das relações estabelecidas pela interação sociedade/natureza. Desta forma, este estudo abrangeu o levantamento dos aspectos geoambientais associando a ocupação do solo e aos usos dos recursos hídricos, bem como à condição de vida de seus habitantes. Foram também analisadas as políticas públicas voltadas a esta questão, identificando o papel que os atores sociais desempenham acerca da gestão hídrica, concluindo com uma proposta local de gestão hídrica. Para tal, foram realizados levantamentos documentais, bibliográficos e de campo, tendo sido elaboradas cartas temáticas acerca dos condicionantes geoambientais, como também a caracterização socioeconômica da bacia por meio de análise exploratória de dados secundários, ambos associados às atividades de campo. Ocupando uma área de 2.559,0 km2, a bacia abrange 14 municípios, dos quais nove apresentam suas sedes municipais inseridas neste recorte espacial. Aspectos climáticos, hidrogeológicos e pedológicos determinam limitações hídricas no Alto e Médio-baixo cursos. Com relação ao uso do solo predominam atividades voltadas para o setor primário da economia. Em termos demográficos, apresenta uma população total em torno de 280 mil habitantes, sendo que a ocupação do seu espaço tem se dado de forma desordenada. Um dos desdobramentos deste fator pode ser constatado na precariedade da infra-estrutura de saneamento básico, na degradação dos mananciais superficiais e na elevada vulnerabilidade socioambiental e hídrica. Não obstante, além de ter sido constatado que a maior parte da população local apresenta renda baixa, associada a um baixo grau de escolaridade, as políticas públicas voltadas para o uso racional dos recursos hídricos nesta bacia ainda são incipientes, sendo explícita a ausência de gestão hídrica. Por fim, constatou-se que a unidade bacia hidrográfica de rio federal apresenta limitações para efetivar a gestão das águas no Vaza Barris sergipano, pois a análise dos condicionantes geoambientais e das condições de vida no referido espaço, exprime a necessidade de um gerenciamento, sobretudo, em nível local.