Abstract This review provides an assessment of the evolution of hydrological modelling for Eastern Africa. We outline the historical development and perspectives considered as this region, like many regions around the world, sees increasing attention on how water resources can be sustainably developed. We emphasize the spatial scales and modelling approaches that typify the region and how these have changed with time. The review is done in two complementary approaches. The first approach is to explore a practical, real-world example providing context for the Eastern Africa region and the water resource development issues presently faced. We use Tanzania's 34 000 km 2 Kilombero Valley (KV) river basin to explore implications of significant gaps in data and modelling scales. We hypothesize that these gaps limit the application of the current state-of-the-science to inform water management policy and practice under current and estimated future conditions. In our second approach, we investigate possible solutions to bridge these gaps through a review of case studies from other Eastern Africa's basins across a range of sizes. Our result highlight that some applications of the models considered under this review anticipated more recent international developments as indicated in Predictions in Ungauged Basins and Panta Rhei initiatives. Through this review, it is clear that there is a possibility to improve understanding of the hydrological processes relevant at scales such as the KV river basin through the use of (1) global precipitation datasets (e.g. satellite and/or homogenized observed data) as input data; (2) remote sensing datasets as model evaluation variable; (3) regionalization around the transferability of model parameters; (4) modification of model codes/structures to suit local conditions; and (5) understanding and application of uncertainty principles in hydrological modelling. Given that many regions of the world face similar water resource management challenges as Eastern Africa; it is likely that the findings of this review could help guide how we develop the next generation of modelling approaches to leverage information from various scales.
Abstract Modeling and observation of ground temperature dynamics are the main tools for understanding current permafrost thermal regimes and projecting future thaw. Until recently, most studies on permafrost have focused on vertical ground heat fluxes. Groundwater can transport heat in both lateral and vertical directions but its influence on ground temperatures at local scales in permafrost environments is not well understood. In this study we combine field observations from a subarctic fen in the sporadic permafrost zone with numerical simulations of coupled water and thermal fluxes. At the Tavvavuoma study site in northern Sweden, ground temperature profiles and groundwater levels were observed in boreholes. These observations were used to set up one‐ and two‐dimensional simulations down to 2 m depth across a gradient of permafrost conditions within and surrounding the fen. Two‐dimensional scenarios representing the fen under various hydraulic gradients were developed to quantify the influence of groundwater flow on ground temperature. Our observations suggest that lateral groundwater flow significantly affects ground temperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlier when a lateral groundwater flux is present. Further, although the thermal regime may be dominated by vertically conducted heat fluxes during most of the year, isolated high groundwater flow rate events such as the spring freshet are potentially important for ground temperatures. As sporadic permafrost environments often contain substantial portions of unfrozen ground with active groundwater flow paths, knowledge of this heat transport mechanism is important for understanding permafrost dynamics in these environments.
Abstract. Students in hydrology are expected to become proficient in a set of quantitative skills, while also acquiring the ability to apply their problem-solving abilities in real-life situations. To achieve both these types of learning outcomes, there is broad evidence that activity-based learning is beneficial. In this paper, we argue that role-play simulations in particular are useful to achieve complex learning outcomes, i.e., making students able to coordinate and integrate various analytical skills in complicated settings. We evaluated the effects of an integrated water resources management (IWRM) negotiation simulation next to more traditional teaching methods intended to foster quantitative understanding. Results showed that despite similar student-reported achievement of both complex and quantitative intended learning outcomes, the students favored the negotiation simulation over the traditional method. This implies that role-play simulations can motivate and actively engage a classroom thereby creating a space for potential deeper learning and longer retention of knowledge. While our findings support the utility of simulations to teach complex learning outcomes and indicate no shortcoming in achieving such outcomes next to traditional methods aimed at quantitative learning outcomes, simulations are still not widely used to foster activity-based learning in the classroom. We thus conclude by presenting three particularly challenging areas of role-play simulations as learning tools that serve as potential barriers to their implementation and suggest ways to overcome such roadblocks.
Artificial subsurface (tile) drainage is used in many agricultural areas where soils have naturally poor drainage to increase crop yield and field trafficability. Studies at the field scale indicate that tile drains disproportionately export large soluble reactive phosphorus (SRP) and nitrate loads to downstream waterbodies relative to other surface and subsurface runoff pathways, but knowledge gaps remain understanding the impact of tile drainage to nutrient export at watershed scales. The Western Lake Erie Basin is susceptible to summertime eutrophic conditions driven by non-point source nutrient pollution due to a shallow mean water depth and land use dominated by agriculture. The purpose of this study is to analyze the impact of tile drainage on downstream discharge, nutrient concentrations, and nutrient loads for 16 watersheds that drain to the Western Lake Erie Basin. Daily discharge and nutrient concentrations were summarized annually and during the main nutrient loading period (March–July) for 2 years representing normal nutrient loading period precipitation (2018) and above normal precipitation (2019). Results indicate positive correlations between watershed tile drainage percentage and runoff metrics during 2019, but no relationship during 2018. Additionally, SRP concentration and load were positively correlated to watershed tile drainage percentage in 2019, but not in 2018. Watershed tile drainage percentage was correlated with nitrate concentration and load for both years. The SRP concentration-discharge relationships suggested relatively weak, chemodynamic behavior, implying a slight enriching effect where SRP concentrations were greater at higher stream discharge conditions during both years. In contrast, nitrate concentration-discharge relationships suggested strong, enriching chemodynamic behavior during 2018, but chemostatic behavior during 2019. The difference in SRP and nitrate export patterns in the 2 years analyzed highlights the importance of implementing appropriate best management practices that target specific nutrients and treat primary delivery pathways to effectively improve downstream aquatic health conditions.
Two different modes of dairy farming intensification in two adjacent sub-watersheds in the headwaters of the South Fork of Sugar Creek in Ohio, USA, are compared with the potential sustainability consequences in connection to landscape structure and patterns as they impact water quality. A survey was administered between 2005 and 2007 in the southern part of the Sugar Creek watershed where we interviewed 28 Amish and non-Amish farmers. We collected data at the field level on farms totaling 3422 ha to characterize intensifications in production under divergent management strategies and to assess the collective implications for the environmental impacts. In addition, water quality was monitored bi-weekly from 2010–2018 using nutrient concentrations at the sub-watershed outlets and in 1998 and 2017 using instream habitat and biological assessments across both sub-watersheds. The main result was that, despite contrasting farming and cropping systems (small versus large farms, animal grazing versus feed), both Amish and non-Amish dairy operations had increased the number of cows and milk per cow on their farms with similar organic nutrient production by animals per hectare farmed. Equally, surface water quality assessed through our monitoring program was similar with both systems showing decreasing nutrient enrichment and increased habitat quality. Interestingly, these equivalent intensifications and environmental impacts were realized despite contrasting demographics and land use patterns found when comparing Amish and non-Amish operations. Collectively, these results illustrate the need to include socio-cultural dimensions to truly capture the trajectory of development as it pertains to the intersection of sustainability and intensification—especially since the complexity of interactions occurring can potentially mask impacts relative to sustainable water resources management.
Abstract. In recent years, there has been increased interest in carbon cycling in natural systems due to its role in a changing climate. Northern latitude systems are especially important as they may serve as a potentially large source or sink of terrestrial carbon. There are, however, a limited number of investigations reporting on actual flux rates of carbon moving from the subsurface landscape to surface water systems in northern latitudes. In this study, we determined dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) fluxes from the subsurface landscape for a sub-arctic catchment located in northern Sweden. These are based on observed annual flux-averaged concentrations of DOC and DIC for the 566 km2 Abiskojokken catchment. We demonstrate the importance to correctly represent the spatial distribution of the advective solute travel times along the various flow and transport pathways. The fluxes of DOC and DIC from the subsurface landscape to the surface water system were comparable in magnitude. This balance could shift under future climatic changes that influence the hydrological and biogeochemical system.
Miniature hyperspectral and thermal cameras onboard lightweight unmanned aerial vehicles (UAV) bring new opportunities for monitoring land surface variables at unprecedented fine spatial resolution with acceptable accuracy. This research applies hyperspectral and thermal imagery from a drone to quantify upland rice productivity and water use efficiency (WUE) after biochar application in Costa Rica. The field flights were conducted over two experimental groups with bamboo biochar (BC1) and sugarcane biochar (BC2) amendments and one control (C) group without biochar application. Rice canopy biophysical variables were estimated by inverting a canopy radiative transfer model on hyperspectral reflectance. Variations in gross primary productivity (GPP) and WUE across treatments were estimated using light-use efficiency and WUE models respectively from the normalized difference vegetation index (NDVI), canopy chlorophyll content (CCC), and evapotranspiration rate. We found that GPP was increased by 41.9 ± 3.4% in BC1 and 17.5 ± 3.4% in BC2 versus C, which may be explained by higher soil moisture after biochar application, and consequently significantly higher WUEs by 40.8 ± 3.5% in BC1 and 13.4 ± 3.5% in BC2 compared to C. This study demonstrated the use of hyperspectral and thermal imagery from a drone to quantify biochar effects on dry cropland by integrating ground measurements and physical models.
Abstract. Permafrost thawing is likely to change the flow pathways taken by water as it moves through arctic and sub-arctic landscapes. The location and distribution of these pathways directly influence the carbon and other biogeochemical cycling in northern latitude catchments. While permafrost thawing due to climate change has been observed in the arctic and sub-arctic, direct observations of permafrost depth are difficult to perform at scales larger than a local scale. Using recession flow analysis, it may be possible to detect and estimate the rate of permafrost thawing based on a long-term streamflow record. We demonstrate the application of this approach to the sub-arctic Abiskojokken catchment in northern Sweden. Based on recession flow analysis, we estimate that permafrost in this catchment may be thawing at an average rate of about 0.9 cm/yr during the past 90 years. This estimated thawing rate is consistent with direct observations of permafrost thawing rates, ranging from 0.7 to 1.3 cm/yr over the past 30 years in the region.
