Exploring the future impacts of urbanization and climate change on groundwater in Arusha, Tanzania

This research article published by Taylor & Francis Online, 2020We combine satellite imagery, urban growth modelling, groundwater modelling and hydrogeological field expeditions to estimate the potential impacts in 2050 of rapid urbanization and climate change on groundwater in Arusha, Tanzania, and by extension similar areas in Sub-Saharan Africa. Our analysis suggests that a reduction of groundwater recharge by 30–44% will cause groundwater levels to drop by up to 75 m, mainly due to increased evapotranspiration and to an expansion in paved surface. If this scenario becomes reality, we predict that wells will run dry, creating health, social and environmental risks

A New Approach for Automatic Extraction of Karst Conduit and Matrix Recession Coefficients

A New Approach for Automatic Extraction of Karst Conduit and Matrix Recession Coefficients Tunde Olarinoye1, Tom Gleeson2, and Andreas Hartmann1 1Department of Hydrological Modelling and Water Resources, University of Freiburg Friedrichstrasse 39 Freiburg Baden Wurttemberg 79098, Germany; 2Department of Civil Engineering, University of Victoria, BC Abstract About 10% of the world’s population gets drinking water from karst groundwater. Groundwater flow in karst aquifers is dynamic and dominated by an interplay of fast and slow flow processes. Managing karst aquifers requires in-depth understanding of hydrogeological behavior. Spring hydrograph recession analysis has been used to understand flow dynamics and characterize karst aquifers for several years. Yet, they have only been applied manually to low numbers of karst spring hydrographs. An automatic recession analysis procedure to analyze large numbers of karst spring hydrographs is still not available. In this study, (1) we evaluate automatic recession extraction methods (REMs), originally developed for stream flow recession analysis for their ability to analyze karst spring hydrographs, (2) we propose simple adaptations of the REMS to allow their application for karst, and (3) we introduce new karst-specific recession analysis models (RAMs) that extract the recession coefficients of conduits and matrix of karst spring hydrographs including an estimation of their uncertainty. We identify the most suitable recession analysis approach by hypothesizing that the most realistic combination of REMs and RAMs provides the most distinguishable pairs of conduit and matrix recession coefficients. We use electric conductivity as an independent source of information to evaluate this hypothesis. Overall, our study will provide new directions for automatic recession analysis of karst systems using adapted extraction methods and karst-specific recession models; and therefore, help to infer about the comparative importance of conduit and matrix drainage in different catchments. Keywords recession analysis, flow dynamics, hydrograph

Integrating field work and large-scale modeling to improve assessment of karst water resources

Comprehensive management of karst water resources requires sufficient understanding of their dynamics and karst-specific modeling tools. However, the limited availability of observations of karstic groundwater dynamics has been prohibiting the assessment of karst water resources at regional to global scales. This paper presents the first global effort to integrate experimental approaches and large-scale modeling. Using a global soil-moisture monitoring program and a global database of karst spring discharges, the simulations of a preliminary global karstic-groundwater-recharge model are evaluated. It is shown that soil moisture is a crucial variable that better distinguishes recharge dynamics in different climates and for different land cover types. The newly developed dataset of karst spring discharges provides first insights into the wide variability of discharge volumes and recharge areas of different karst springs around the globe. Comparing the model simulations with the newly collected soil-moisture and spring-discharge observations, indicates that (1) improvements of the recharge model are still necessary to obtain a better representation of different land cover types and snow processes, and (2) there is a need to incorporate groundwater dynamics. Applying and strictly evaluating these improvements in the model will finally provide a tool to identify hot spots of current or future water scarcity in the karst regions around the globe, thus supporting national and international water governance.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/50110000165

Global karst springs hydrograph dataset for research and management of the world’s fastest-flowing groundwater

Karst aquifers provide drinking water for 10% of the world’s population, support agriculture, groundwater-dependent activities, and ecosystems. These aquifers are characterised by complex groundwater-flow systems, hence, they are extremely vulnerable and protecting them requires an in-depth understanding of the systems. Poor data accessibility has limited advances in karst research and realistic representation of karst processes in large-scale hydrological studies. In this study, we present World Karst Spring hydrograph (WoKaS) database, a community-wide effort to improve data accessibility. WoKaS is the first global karst springs discharge database with over 400 spring observations collected from articles, hydrological databases and researchers. The dataset’s coverage compares to the global distribution of carbonate rocks with some bias towards the latitudes of more developed countries. WoKaS database will ensure easy access to a large-sample of good quality datasets suitable for a wide range of applications: comparative studies, trend analysis and model evaluation. This database will largely contribute to research advancement in karst hydrology, supports karst groundwater management, and promotes international and interdisciplinary collaborations

Global karst springs hydrograph dataset for research and management of the world’s fastest-flowing groundwater

Karst aquifers provide drinking water for 10% of the world’s population, support agriculture, groundwater-dependent activities, and ecosystems. These aquifers are characterised by complex groundwater-flow systems, hence, they are extremely vulnerable and protecting them requires an in-depth understanding of the systems. Poor data accessibility has limited advances in karst research and realistic representation of karst processes in large-scale hydrological studies. In this study, we present World Karst Spring hydrograph (WoKaS) database, a community-wide effort to improve data accessibility. WoKaS is the first global karst springs discharge database with over 400 spring observations collected from articles, hydrological databases and researchers. The dataset’s coverage compares to the global distribution of carbonate rocks with some bias towards the latitudes of more developed countries. WoKaS database will ensure easy access to a large-sample of good quality datasets suitable for a wide range of applications: comparative studies, trend analysis and model evaluation. This database will largely contribute to research advancement in karst hydrology, supports karst groundwater management, and promotes international and interdisciplinary collaborations

Integrating field work and large-scale modeling to improve assessment of karst water resources

Comprehensive management of karst water resources requires sufficient understanding of their dynamics and karst-specific modeling tools. However, the limited availability of observations of karstic groundwater dynamics has been prohibiting the assessment of karst water resources at regional to global scales. This paper presents the first global effort to integrate experimental approaches and large-scale modeling. Using a global soil-moisture monitoring program and a global database of karst spring discharges, the simulations of a preliminary global karstic-groundwater-recharge model are evaluated. It is shown that soil moisture is a crucial variable that better distinguishes recharge dynamics in different climates and for different land cover types. The newly developed dataset of karst spring discharges provides first insights into the wide variability of discharge volumes and recharge areas of different karst springs around the globe. Comparing the model simulations with the newly collected soil-moisture and spring-discharge observations, indicates that (1) improvements of the recharge model are still necessary to obtain a better representation of different land cover types and snow processes, and (2) there is a need to incorporate groundwater dynamics. Applying and strictly evaluating these improvements in the model will finally provide a tool to identify hot spots of current or future water scarcity in the karst regions around the globe, thus supporting national and international water governance

Global karst springs hydrograph dataset for research and management of the world’s fastest-flowing groundwater

(IF 6.44; Q1)International audienceKarst aquifers provide drinking water for 10% of the world’s population, support agriculture, groundwater-dependent activities, and ecosystems. These aquifers are characterised by complex groundwater-flow systems, hence, they are extremely vulnerable and protecting them requires an in-depth understanding of the systems. Poor data accessibility has limited advances in karst research and realistic representation of karst processes in large-scale hydrological studies. In this study, we present World Karst Spring hydrograph (WoKaS) database, a community-wide effort to improve data accessibility. WoKaS is the first global karst springs discharge database with over 400 spring observations collected from articles, hydrological databases and researchers. The dataset’s coverage compares to the global distribution of carbonate rocks with some bias towards the latitudes of more developed countries. WoKaS database will ensure easy access to a large-sample of good quality datasets suitable for a wide range of applications: comparative studies, trend analysis and model evaluation. This database will largely contribute to research advancement in karst hydrology, supports karst groundwater management, and promotes international and interdisciplinary collaborations