Transboundary Watershed Research Articles

The relationship between land use change and flood flows, a case study in a transboundary watershed

Introduction: Introduction: The HEC-HMS model was applied in the transboundary basin of the Zarumilla River (Ecuador – Peru) to simulate the flows that would occur during maximum precipitation events. Methodology: The model integrated the precipitation determined by intensity equations, the infiltration defined by the curve number, the rain - runoff transformation by unit hydrographs, the hydrological routing calculated by applying Muskingum - Cunge and was calibrated by a frequency analysis using the hydrometric information available. Results: The model was executed satisfactorily and the resulting maximum flows at the outlet of the basin varied between 1.100 m3/s and 1.670 m3/s depending on the return period. A land use scenario for the year 2027 was generated using information from 2014 and 2017 that was evaluated with the model. Discussion: The transitions with the largest area of influence observed were pasture to crop, forest to crop and crop to pasture. Other classifications do not present a significant change. Conclusions: The flows calculated with the coverage of the generated scenario are lower than those calculated for 2017, due to the expansion of crops, which are mostly fruit crops. Despite this, the variation in flow rates was not very significant.

Public opinion risk perception of decision makers’ in transboundary watershed emergency water supply

ABSTRACT In recent years, the number of public opinion risks related to sudden transboundary drought events has continued to increase. Research on the perception of public opinion risks has become an indispensable and increasingly important part of emergency management research in transboundary watersheds. Based on relevant literature and interview materials, an exploratory theoretical construction was conducted using the grounded theory research method. The research results indicate that four main categories of public opinion risks, namely, political, economic, ecological and environmental, and socio-cultural, have a significant impact on the perception of public opinion risks among decision-makers in transboundary watershed emergency water supply. The formation mechanisms of decision-makers’ perception of public opinion risks vary in each of these four categories. This research not only enriches the relevant research on the influencing factors of decision-makers’ perception of public opinion risks in theory but also provides decision-making reference and guidance for transboundary watershed water resource management in practice.

Quantitative simulation of ecological compensation approaches in transboundary watersheds of China: A scenario analysis based on a multi-regional CGE model

Watershed ecological compensation is becoming increasingly important as an effective way to achieve transboundary watershed governance. The large regional differences in economic development and watershed governance across China require the implementation of regionally differentiated policies. Previous studies have not systematically examined the potential impacts of ecological compensation approaches at the regional scale in China. As the Beijing-Tianjin-Hebei region is representative of China with severe watershed problems, the establishment of a watershed ecological compensation mechanism in this region has a demonstrated effect on solving regional co-management problems. By establishing a multi-regional dynamic CGE (Computable General Equilibrium) model with water quality and quantity control as constraints, the long-term impacts of different ecological compensation methods on different districts are assessed in terms of economic development, social welfare and water environment management, based on which the preferred compensation methods for the development of the three districts and the whole region are to be identified. The study shows that: Ⅰ) Different compensation approaches have varying impacts on regional ecology and economy, and trade-offs need to be made between the two to choose the appropriate compensation approach to provide a long-term incentive for regional watershed governance and maintenance; Ⅱ) The compensating areas prefer short-term compensation such as financial subsidies, while the compensated areas prefer long-term compensation such as industrial support; Ⅲ) Financial funds can support the development of primary and secondary industries in the short term, and subsidies to enterprises contribute to the overall economic synergy of the region, while industrial support from compensating areas to compensated area requires long-term layout. Accurate measurement of the potential impacts of different ecological compensation approaches can provide a scientific basis for the establishment of a long-term ecological compensation mechanism, and the model can also be applied to other regional policies to provide a reference for solving transboundary governance issues.

Evaluation of bias correction methods for a multivariate drought index: case study of the Upper Jhelum Basin

Abstract. Bias correction (BC) is often a necessity to improve the applicability of global and regional climate model (GCM and RCM, respectively) outputs to impact assessment studies, which usually depend on multiple potentially dependent variables. To date, various BC methods have been developed which adjust climate variables separately (univariate BC) or jointly (multivariate BC) prior to their application in impact studies (i.e., the component-wise approach). Another possible approach is to first calculate the multivariate hazard index from the original, biased simulations and bias-correct the impact model output or index itself using univariate methods (direct approach). This has the advantage of circumventing the difficulties associated with correcting the inter-variable dependence of climate variables which is not considered by univariate BC methods. Using a multivariate drought index (i.e., standardized precipitation evapotranspiration index – SPEI) as an example, the present study compares different state-of-the-art BC methods (univariate and multivariate) and BC approaches (direct and component-wise) applied to climate model simulations stemming from different experiments at different spatial resolutions (namely Coordinated Regional Climate Downscaling Experiment (CORDEX), CORDEX Coordinated Output for Regional Evaluations (CORDEX-CORE), and 6th Coupled Intercomparison Project (CMIP6)). The BC methods are calibrated and evaluated over the same historical period (1986–2005). The proposed framework is demonstrated as a case study over a transboundary watershed, i.e., the Upper Jhelum Basin (UJB) in the Western Himalayas. Results show that (1) there is some added value of multivariate BC methods over the univariate methods in adjusting the inter-variable relationship; however, comparable performance is found for SPEI indices. (2) The best-performing BC methods exhibit a comparable performance under both approaches with a slightly better performance for the direct approach. (3) The added value of the high-resolution experiments (CORDEX-CORE) compared to their coarser-resolution counterparts (CORDEX) is not apparent in this study.

Spatial and Temporal Water Quality Data Prediction of Transboundary Watershed Using Multiview Neural Network Coupling

Spatial and Temporal Water Quality Data Prediction of Transboundary Watershed Using Multiview Neural Network Coupling

Environmental Economic Diplomacy Approach in International Law of Transboundary Water Sharing

In this article, the existing international laws in the field of transboundary waters, as well as water treaties and the approaches used to resolve disputes, have been reviewed and analyzed by using international documents and information. 
 As international convention’s provisions, every state in the common river basin has the right to have fair and reasonable exploitation of the water flow of the transboundary watershed in its territory, with the obligation not to cause damage to other countries. This right is determined by considering the natural factors of the watershed, existing and potential uses, social and economic needs of the countries of the basin, and the effects of exploitation on other countries. But the factors presented for this purpose are general and have different technical and legal interpretations.

Phosphorus and nitrogen deposition within a large transboundary watershed: Implications for nutrient stoichiometry and lake vs watershed budgets

Atmospheric deposition is an important source of both phosphorus (P) and nitrogen (N) to lakes and their watersheds, but the two nutrients are rarely reported together. For the first time, we measured total P (TP) and N (total, ammonium, NH4-N and nitrate, NO3-N) bulk deposition to the Lake of the Woods (LoW) watershed, a large international lake that experiences frequent, lake-wide cyanobacterial blooms. Phosphorus deposition was highly variable both spatially and seasonally, with on average >75 % of annual deposition occurring in the spring and summer months, associated with local biogenic input. In contrast, winter TP deposition was relatively low and spatially invariant, and not affected by local sources. Importantly, these results suggest that P deposition may be a much larger source of input to the LoW as a result of its tortuous shoreline and abundance of forested islands (>5000), which are concentrated in the northern, Canadian waters and greatly extend the ‘shoreline influence’ within this lake. We suggest that a single annual TP load estimate is not appropriate for the LoW because winter deposition is likely much lower than past estimates whereas spring/summer deposition is substantially higher and could be an important, but previously unrecognized source, of bioavailable P to the nearshore waters. Further research is needed on the spatial and temporal patterns of P vs N deposition to the lake surface and their influence on primary productivity and algal species composition.

Application of remote sensing and GIS to assess groundwater potential in the transboundary watershed of the Chott-El-Gharbi (Algerian–Moroccan border)

Remote sensing (RS) and Geographic Information Systems (GIS) have become widely used in various fields around the world in recent years. In this paper; we attempt to delineate the groundwater potential zone in the transboundary watershed of Chott-El-Gharbi using the integration of RS, GIS methods. Eight influencing thematic layers viz. geology, rainfall, water table level, lineaments density, slope, drainage density, elevation, and land use/land cover were used. Afterward, Analytical Hierarchy Process technique, which offers good functionality for mapping the groundwater potentiality was used, where ranks and weights, assigned to each factor are computed statistically, based on their relative importance in terms of groundwater potential. Then, groundwater potential zones are classified into five categories namely excellent, high, medium, low, and very low zone, which represent 964.48 km2 (7.33%), 1467.30 km2 (11.15%), 7969.51 km2 (60.57%), 2639.52 km2 (20.06%), and 116.19 km2 (0.88%) of the study area, respectively. The very low potential region is found in the southern region of the study area, which is covered by mountains. Moreover, excellent groundwater potential zones are located at the central part of the region of Chott, which has quaternary formations where the infiltration is high. On the other hand, moderate and poor groundwater potential zones cover by the bare lands in the study area. Finally, the results were carefully validated with the yields data of various boreholes in the study area, which reveals an accuracy achievement of 72.41%. The finding of this research constitutes a valuable contribution towards the water resources management, and it forms a significant decision support tool for equitable and sustainable utilization of groundwater resources in the transboundary watershed of Chott-El-Gharbi. The study's findings will also serve as a benchmark for future research and studies, such as hydrogeological modeling.

Integrating Urban Planning and Water Management Through Green Infrastructure in the United States-Mexico Border

Creating sustainable, resilient, and livable cities calls for integrative approaches and collaborative practices across temporal and spatial scales. However, practicability is challenged by institutional, social, and technical complexities and the need to build collective understanding of integrated approaches. Rapid urbanization along the United States-Mexico border, fueled by industrialization, trade, and migration, has resulted in cities confronted with recurrent flooding risk, extended drought, water pollution, habitat destruction and systemic vulnerabilities. The international border, which separates natural and built ecosystems, is both a challenge and an opportunity, making a unique social and institutional setting ideal for testing the integration of urban planning and water management. Our research focuses on fusing multi-functional and multi-scalar green infrastructure to restore ecosystem services through a strategic binational planning process. This paper describes this planning process, including the development and application of both a land suitability analysis and a hydrological model to optimally site green infrastructure in the Nogales, Arizona, United States—Nogales, Sonora, Mexico, cross border region. We draw lessons from this process and stakeholder feedback focused on the potential for urban green infrastructure, to allow for adaptation and even transformation in the face of current and future challenges such as limited resources, underdeveloped governance, bordering, and climate change. In sum, a cross border network of green infrastructure can provide a backbone to connect this transboundary watershed while providing both hydrological and social benefits.

Exploring the Spatio-Temporal Variability of Precipitation over the Medjerda Transboundary Basin in North Africa

Medjerda is a key transboundary watershed in the Maghreb region, crossing from the Algerian mountains through northern Tunisia. Therefore, the analysis of the rainfall regime in this basin is of paramount importance for water resources management and regional economic development, notably concerning agriculture. This study examines the rainfall trends over the Medjerda watershed on multi-temporal scales (monthly, seasonally and annually) with a database of monthly rainfall observed in 60 stations evenly spread over the watershed. After filling gaps and homogenizing data, the Mann–Kendall test for trend detection was applied to rainfall series and the Sen’s slope method was adopted to estimate the trend’s magnitude, interpolated over the sub-catchments, to analyze the spatial distribution of rainfall changes within the watershed. Results showed the absence of significant trends at the annual scale for the entire catchment. However, rainfall redistribution was observed throughout the year, with a notable precipitation reduction during spring and increased winter precipitation, which could impact agriculture and ecosystem functioning. This modification of the rainfall regime implies an adaptation of the management of dams and reservoirs, with a reduced filling capacity during spring in anticipation of the summer dry season.

Assessment of Meteorological Drought in Climate Variability Context within the Comoe River Transboundary Watershed

In the context of climate variability resulting in a decrease in rainfall with a severe drought, a spatio-temporal study of this phenomenon remains imperative for the efficient management of water resources. This paper aims to assess the long-term rainfall drought trend and breakpoints within the Comoe River watershed. From monthly rainfall data series (1960-2000), Standardized Precipitation Index (SPI) values were calculated for a time scale of 3 months (SPI.3). Statistical tests for breaks (CUSUM, and t-Student) and trends (Man-Kendall and Linear Regression) as well as the Sen’ slope method for estimating the magnitude of trends was applied. The breaks dates observed are mostly located after the 1970s. Based on SPI.3 values below the threshold of 0.84 chosen as an indicator of drought, rarely has more than half of the catchment area been affected by drought. The average watershed affected is about 20% over the study period (1960-2000). The most representative years, in terms of spatial expansion of the drought, in decreasing order of importance are: 1983, 1992, 1972 and 1982. The years 1982 and 1983 stand out for their exceptional condition, as the drought-affected 50% to 90% of the total catchment area. SPI.3 series from 1960 to the various break dates recorded slopes between -0.01 and 0.00 with a slight drought trend for most of the catchment. After the break periods, almost the entire northern part of the basin is characterized by slight moisture with Sen’s slopes between 0.000 and 0.005. The southern part will remain slightly subject to normal rainfall conditions.

Estimation of Annual Runoff of Galal Badra Transboundary Watershed Using Arc Swat Model, Wasit, Eastern of Iraq

Optimal investment of natural water resources in an area is an effective way to provide significant amounts of water that can contribute to reduce the negative impacts of climate extremism. Proper assessment of the components of any hydrological system is a priority in watersheds studying. SWAT (Soil and Water Assessment Tool) model was used within ArcGIS, to assess the hydrological situation in general, and surface runoff in particular for Galal Badra Watershed GBW (Wasit Governorate, eastern Iraq). GBW has an area of 2,655 square kilometers (89% of which is in Iran and the rest 11% within Iraq). The data set for SWAT model running were digital elevation model, slope map, soil map, LULC map, and climatic data (precipitation, relative humidity, wind speed, solar radiation, minimum/ maximum air temperature). SWAT simulation concluded that the annual average surface runoff in GBW was 244x106 cubic meters (with an average discharge of 7.8 M3 / s), which accounts for about 25.7% of the total precipitation. This ratio can be used in preliminary forecasting of surface runoff resulting from different amounts of precipitation. The model was not calibrated due to insufficient data available to complete the calibration process. However, the results provided by the SWAT model regarding the water balance elements in the watershed, make the SWAT model an effective tool for hydrological assessments, especially in cases where the necessary data are scarce for various reasons. Also, SWAT results can be considered as a preliminary assessment, which gives an overview of the hydrological situation of the area, contributes to building an initial perception of the water system, determining the most important elements in it, and anticipating the factors most influencing it. This enables policymakers, decision-makers, and stakeholders to adopt future plans at the level of research and implementation that will develop the reality of water investment in the region under conditions of climate extremism.

A GIS-MCDA-Based Suitability Analysis for Meeting Targets 6.3 and 6.5 of the Sustainable Development Goals

Among the Sustainable Development Goals (SDGs) established in the 2030 Agenda, goals 6.3, regarding clean water and improve of water quality, and 6.5, regarding integrated water resources management, highlight the need for the implementation of successful environmental water quality monitoring programs of transboundary river waterbodies. In the present study, the designation of high priority areas for water quality monitoring of Drin transboundary watershed is performed using a suitability model, a GIS-based multicriteria decision analysis (GIS-MCDA) approach that takes into consideration the most important conditioning factors that impose pressures on rivers. Based on the results, the methodological approach used manages to sufficiently delimit the areas with increased need for water quality monitoring in the Drin watershed, and the validation procedure produces a correlation coefficient of 0.454 (statistically significant at a 0.01 level). Limitations arise in the case of a lack of detailed information or inaccurate input data and due to the inconsistency among the input data and the different methodological approaches regarding the information collection of each country involved. These restrictions foreground the need for cooperation between the countries involved regarding the exchange of scientific knowledge and common legislation, so as to achieve integrated, effective, and sustainable management of water resources of the area.

On Care for Our Common Home: Ecological Materiality and Sovereignty over the Lempa Transboundary Watershed

AbstractFor over a decade, Salvadorean grassroots movements and non-governmental organisations (NGOs) pursued legal innovations with the aim of protecting their water sources from potentially polluting industrial activities such as mining. They initially drafted bans on mining that would preclude the extractive-based development path embraced by neighbouring countries. Eventually, they scaled up their approach and devised a draft proposal for a transboundary waters treaty that addressed the challenges that the ecological materiality of international watercourses poses to nationalde juresovereignty. In so doing, the transboundary watershed has become a useful heuristic, a spatial trope to which Salvadoreans have turned to substantiate their claims to sovereignty over the Lempa River waters that El Salvador shares with pro-mining Guatemala and Honduras – claims imbued with an ethics of care rooted in wartime politics and Catholic morality.

Multidimensional trust and its impact on the willingness to pay for ecological compensation in China’s transboundary watersheds—taking the largest tributary of the Yellow River as an example

Transboundary watershed ecological compensation in China is a kind of trust-based cooperation between the upstream and downstream. However, existing research does not further detail multidimensional trust to explore its impact on willingness to pay (WTP). From the perspective of multidimensional trust, it is helpful to clarify the internal motivations for public participation, so as to realize the transformation from current government-led economic incentive mode to normative guidance of effective social behavior. Combined with the specific background of China’s ecological compensation, this study divides the downstream public trust into three dimensions: trust in self-governance capabilities, trust in upstream governance capabilities, and trust in local government. The empirical results show that the downstream trust in their own governance ability has a positive impact on their WTP, and when the downstream trust in the upstream governance capacity, the higher their WTP. Moreover, the more trust the local government, the higher the WTP.

Climate change literature and information gaps in mountainous headwaters of the Columbia River Basin

Climate change is altering mountainous headwaters and the biophysical and social systems that depend on them. While scientific knowledge on climate change abounds, literature syntheses are needed to understand the multidisciplinary impacts, identify critical knowledge gaps, and assess potential management and policy responses. In this study, we systematically map and analyze the topical and spatial distribution of climate change research in the mountainous headwaters of a major transboundary watershed, the Columbia River Basin (CRB). We find that climate change research in the CRB focuses on impacts much more frequently than adaptation, while mitigation is rarely a focus. Most studies assess trends at large spatial extents, use secondary data, and make projections of climate change impacts rather than observations. The spatial distribution and thematic content of research vary across an international border, with greater concentrations of research in the USA than Canada. A general scarcity of social science research and limited interaction between social and biophysical content reinforce the need for increased collaboration between disparate disciplines. Future research focus areas should include research related to climate change adaptation and mitigation, increased integration between social and biophysical sciences, and collaborations that bridge the international border for a more unified basin-wide focus. Focusing on these new directions for research will increase the potential for science and management communities to co-produce actionable science and effective responses to climate change.

Guiding riparian management in a transboundary watershed through high resolution spatial statistical network models

The United States Environmental Protection Agency and the Houlton Band of Maliseet Indians (HBMI) built a stream temperature spatial statistical network (SSN) model for the Meduxnekeag Watershed. The headwaters of the Meduxnekeag Watershed are in Maine, United States of America and the outlet is in New Brunswick, Canada, creating an additional challenge because many datasets are constrained to political boundaries. The release of the High-Resolution National Hydrology Dataset Plus included transboundary watersheds and enabled creation of fine resolution (1:24,000) SSN temperature models consistent with management scales for riparian buffers. SSN models were developed for July, August, and September median stream temperatures and the growing season maximum (GSM). Fitted SSN models had relatively high R2 values (0.88–0.96) and all final models included significant parameters for shade-attenuated solar radiation, reference flow, air temperature, and bankfull depth or width. Fitted models predicted stream temperatures during a dry (2010) and wet (2011) year. Monthly models predicted the fewest cold water (<19.0 °C) reaches in July with 28% in the dry and 68% in the wet year. September had >99% cold water reaches, and August results were intermediate between July and September. GSM predictions found 81% of stream reaches could not support salmonid survival (>27.0 °C) in the dry year and 59% of the reaches were warmwater (22.5–27.0 °C) in the wet year. The model was used to predict stream temperatures following restoration scenarios of a forested 30-m or 90-m buffer of stream segments bordered by agricultural or developed land. The restoration scenarios expanded cold water habitat based on monthly median temperatures and decreased the habitat area with GSM above survival thresholds, with little difference in effectiveness of the two buffer widths. These results will guide riparian restoration projects by the HBMI to expand habitat for cold water fishes.

Key components and contrasts in the nitrogen budget across a US-Canadian transboundary watershed.

Watershed nitrogen (N) budgets provide insights into drivers and solutions for groundwater and surface water N contamination. We constructed a comprehensive N budget for the transboundary Nooksack River Watershed (British Columbia, Canada and Washington, US) using locally-derived data, national statistics and standard parameters. Feed imports for dairy (mainly in the US) and poultry (mainly in Canada) accounted for 30 and 29% of the total N input to the watershed, respectively. Synthetic fertilizer was the next largest source contributing 21% of inputs. Food imports for humans and pets together accounted for 9% of total inputs, lower than atmospheric deposition (10%). N imported by returning salmon representing marine derived nutrients accounted for <0.06 % of total N input. Quantified N export was 80% of total N input, driven by ammonia emission (32% of exports). Animal product export was the second largest output of N (31%) as milk and cattle in the US and poultry products in Canada. Riverine export of N was estimated at 28% of total N export. The commonly used crop nitrogen use efficiency (NUE) metric alone did not provide sufficient information on farming activities but in combination with other criteria such as farm-gate NUE may better represent management efficiency. Agriculture was the primary driver of N inputs to the environment as a result of its regional importance; the N budget information can inform management to minimize N losses. The N budget provides key information for stakeholders across sectors and borders to create environmentally and economically viable and effective solutions.

A Metacoupling Framework for Exploring Transboundary Watershed Management

Water is crucial for ecosystem health and socioeconomic development, but water scarcity is becoming a global concern. Management of transboundary watersheds is inherently challenging and has the potential to lead to conflict over the allocation of water resources. The metacoupling framework, which explores the relationships between coupled human and natural systems that are nested within multiple different scales, has been proposed to inform more holistic management of transboundary watersheds. This paper provides the first attempt to apply a metacoupling framework to a transboundary watershed for an improved integrated understanding of this complex system at multiple spatial scales. It does so with the transnational Limpopo River watershed in Southern Africa, which covers 1.3% of the continent and supports the livelihoods of 18.8 million people living in Botswana, Mozambique, South Africa, and Zimbabwe. Sub-Saharan Africa is experiencing a growing gap between water availability and demand; the primary drivers are population growth and agriculture expansion. The novelty of the paper is outlining the importance of applying a metacoupling framework to transboundary watersheds, identifying the limitations to this application, and providing a detailed assessment of the steps needed to complete this application. We also identify directions for future research including application of a metacoupling framework to other transboundary watersheds and exploration of spillover effects and externalities within this and other transboundary watersheds.

Integrated assessment of extreme climate and landuse change impact on sediment yield in a mountainous transboundary watershed of India and Pakistan

Assessment of climate and land use changes impact including extreme events on the sediment yield is vital for water and power stressed countries. Mangla Reservoir is the second-largest reservoir in Pakistan, and its capacity is being reduced due to rapid sedimentation and will be threatened under climate and land use changes. This paper discusses the consequences of climate and land use change on sediment yield at Mangla Dam using General Circulation Models (GCMs), Land Change Modeler (LCM), Soil and Water Assessment Tool (SWAT) model after calibration and validation. Results show that over the historical period temperature is observed to increase by 0.10oC/decade and forest cover is observed to reduce to the level of only 16% in 2007. Nevertheless, owing to the forest conservation policy, the forest cover raised back to 27% in 2012. Anticipated land use maps by using LCM of 2025, 2050 and 2100 showed that the forest cover will be 33%, 39.2%, and, 53.7%, respectively. All seven GCMs projected the increase in temperature and five GCMs projected an increase in precipitation, however, two GCMs projected a decrease in precipitation. Owing to climate change, land use change and combined impact of climate and land use change on annual sediment yield (2011-2100) may vary from -42.9% to 39.4%, 0% to -27.3% and, -73% to 39.4%, respectively. Under climate change scenarios projected sediment yield is mainly linked with extreme events and is expected to increase with the increase in extreme events. Under land use change scenarios projected sediment yield is mainly linked with the forest cover and is expected to decrease with the increase in forest cover. The results of this study are beneficial for planners, watershed managers and policymakers to mitigate the impacts of climate and land use changes to enhance reservoir life by reducing the sediment yield.