Catchment Management Research Articles

Hybrid model approach for hilly sub-watershed prioritization using morphometric parameters: a case study from Bakkhali river watershed in Cox’s Bazar, Bangladesh

ABSTRACT This study investigates the morphometry of the Bakkhali watershed (BW) in the hilly districts of Cox’s Bazar and Bandarban, Bangladesh, to analyze its hydrological characteristics. Morphometric parameters were utilized to prioritize sub-watersheds (SWs) through a hybrid approach combining principal component analysis (PCA) and the weighted-sum approach (WSA). Using ArcGIS Pro 2.7.0, streams, the watershed, and SWs were delineated from a 30-m resolution COP30 DEM. Preliminary priority ranks (PPR) were determined based on direct and inverse relationships of morphometric parameters to soil erodibility. Weighted compound factors (CF) were calculated from PCA results for final prioritization. The BW, a fifth-order watershed with a drainage area of 571.52 km², shows a consistent decrease in the number of streams with increasing stream order, indicating an erosional landform. The mean bifurcation ratio of 4.09 suggests a higher tendency for soil erosion. Shape factors indicate an elongated watershed with less pronounced peak flow characteristics. The analysis identified SW2 and SW3 as high-erosion zones, SW4 and SW9 as medium-erosion zones, and SW1 as a low-erosion zone. The study demonstrates the efficacy of combining geospatial and statistical tools for SW prioritization.

PENGENDALIAN BANJIR SUNGAI BENGKANG UNTUK MENDUKUNG KAWASAN EKONOMI KHUSUS MANDALIKA

Changes in land use that have occurred over a period of several years in the Kuta area have resulted in a lack of water catchment areas. The impacts caused by the lack of catchment areas are flooding and reduced water quality in rivers. The flood disaster in the Bengkang River caused damage to bridge infrastructure and people’s homes. The Bengkang river basin is divided into 3 sub – basins with a total area of 10,45 km2. Based on the results of the design flood analysis using the Nakayasu synthetic unit hydrograph method, the largest flood discharge value was obtained, namely 32,859 m3/second for a return period of 25 years. Hydraulic modeling was carried out to determine the water level and the ability of the river section to receive flow using HEC-RAS 6.1 software. Based on the simulation results with a return period of 5 years, it is known that flooding occurs in the middle and lower reaches of the Bengkang River, so structural mitigation is needed, namely normalization and repair of embankments. A 25-year return period flow simulation was carried out using a cross – section of the channel plan and no runoff was obtained in the Bengkang River.

Using δ65Cu and δ34S to determine the fate of copper in stream waters draining porphyry mineralization: Implications for exploration targeting

The fate of metals, such as Cu, in stream waters draining porphyry mineralization is commonly controlled by several natural processes such as sorption, microbial processes, and ligand availability. Isotopes of Cu offer a novel approach to understanding these processes and determining metal sources within complicated mineralogical systems. Drainages at the Casino Cu-Au-Mo porphyry deposit, Yukon, Canada exhibit circumneutral (pH > 5) in Casino Creek and natural acid rock drainage (pH < 3.5) in Proctor Gulch with the precipitation of schwertmannite (Fe3+). Isotopic systems δ65Cu and δ34Ssulfate indicate different metal sources, with signatures of both hypogene and supergene mineralization. Waters from Proctor Gulch contain δ65Cu values (< −0.5 ‰) consistent with supergene Cu sources from the leached or oxide portion of the mineralization. Comparatively, drainage in the upper part of Casino Creek contains a δ65Cu composition (> 0.5 ‰) characteristic of Cu sourced from hypogene sulfide mineral oxidation. Variation in metal sources is similarly supported by aqueous δ34Ssulfate values in the stream waters, which suggest mixing of S derived from a sulfide mineral phase and a much heavier sulfate mineral (e.g., gypsum or anhydrite). Isotopic fractionation of Cu in the dissolved (<0.45 μm) phase presents two predominant controls on Cu dispersion. The natural acid conditions in Proctor Gulch favor the preferential co-precipitation of 63Cu with schwertmannite but could be influenced by intracellular assimilation or adsorption by microbes, which also has been shown to preferentially favor 63Cu. Copper isotopic fractionation results in a gradient of increasing δ65Cu values in waters downstream. In Casino Creek, higher pH conditions favor the precipitation of Fe(OH)3 and the preferential adsorption of 65Cu, resulting in decreasing δ65Cu values downstream. Copper concentrations in stream waters remain elevated (up to 4.1 μg/L) above ambient background (1.9 μg/L) levels up to 11 km downstream of the deposit. Given the abundance of surface water in many parts of northern Canada, hydrogeochemical prospecting using broad scale stream water catchment analysis is clearly a viable greenfield exploration methodology.

Aquifer Exploration Using the Resistivity Method with a Schlumberger Arrays in Sangubanyu Sub-Village, Banyuwangi Village, Bandongan Subdistrict, Magelang Regency

Sangubanyu sub-vilage is administratively located in Banyuwangi Village, Bandongan Subdistrict, Magelang Regency. During the dry season, it is common to find dry wells in the community, making it difficult for residents to access clean water. This situation is highly ironic, as Magelang Regency generally experiences high rainfall, is situated in the Progo and Bogowonto river basins, and is surrounded by mountains that, theoretically, act as water catchment areas. The investigation of aquifer depth was conducted using the Vertical Electrical Sounding (VES) method with a Schlumberger electrode configuration, which is used to map the vertical distribution of subsurface resistivity. VES field data collection was carried out at two measurement points using two current electrodes and two potential electrodes. The electrode spread at each measurement point was 400 meters. The sounding data from each measurement point was interpreted using IP2win software version 3.01, and the results were presented as resistivity logs showing resistivity values, depths, and the thickness of each layer. The interpretation results yielded a 1D resistivity model, showing variations in resistivity with depth. The aquifer layer was identified as sandy tuff with resistivity values ranging from 17 Ωm to 21 Ωm at depths of approximately 33 to 78 meters.

Methane degassing in global river reservoirs and its impacts on carbon budgets and sustainable water management

Degassing methane (CH4) through reservoir water compromises hydroelectricity's presumed low-carbon status, which has emerged as a critical hotspot for global carbon dynamics. However, a comprehensive understanding of the involved pathways remains elusive, hindering the accurate estimation of global reservoirs' carbon budget (emission-to-burial ratio). This study presents a holistic upscaling approach to assess methane degassing in global river reservoirs and its impacts on carbon budgets. Firstly, a machine learning model is utilized to characterize the contributions of climate and human factors to annual water residence time. Secondly, the stepwise multiple linear regression method is used to calculate CH4 degassing emissions for each reservoir. Finally, to systematically tackle all sources of uncertainty, separate uncertainty analyses are implemented for the estimates of degassing emissions, areal emissions, and organic carbon burial. Analyzing 30-year data from 6695 reservoirs worldwide, our assessment considers water residence time, temperature, catchment area, and reservoir size. Findings indicate that water releases contribute significantly to global CO2 emissions from reservoirs, elevating the carbon budget by 20 % from 2.02 to 2.18 TgC/year, underscoring the previously underestimated significance of CH4 degassing in shaping the carbon cycle impact of river reservoirs. We propose a redefined threshold for low carbon credits, suggesting that reservoirs with power densities exceeding 6.1 MW/km2, instead of the conventional 4 MW/km2, should qualify. This study underscores the need for sustainable water management and reshaping the carbon dynamics associated with hydroelectricity. Future research can advocate Artificial Intelligence (AI) techniques to enhance water management and mitigate carbon emissions by multi-objectively optimizing reservoir operations.

Large wetlands representation in SWAT+: the case of the Pantanal in the Paraguay River Basin

The Paraguay River Basin forms part of the La Plata River Basin in South America. Its streamflow is significantly attenuated by a high evapotranspiration rate, very gentle slopes and the presence of a vast wetland known as the Pantanal. Modeling the hydrology of watersheds in which the flood pulse is affected by the presence of large floodplains can pose issues for hydrological models that do not account for spatial complexity and simplify water routing using linear assumptions. The new version of the Soil and Water Assessment Tool, known as SWAT+, routes water using variations of the kinematic wave model. However, with the inclusion of connectivity and Landscape Units, SWAT+ provides more flexibility in terms of representing the hydrologic fluxes in the watershed. The main objective of this study is to use the concept of Landscape Units and connectivity to represent the water exchanges between uplands, floodplains and channels. We developed code routines to (1) temporally retain surface and subsurface water coming from the upland into the floodplain, by assuming a reservoir-like floodplain behavior, and (2) represent overbank flow, aiming to fully simulate the interactions between channels and floodplains. The model was calibrated based on monthly discharge for the period 1990 to 2020. The simulated average annual water storage in the floodplains of the Paraguay River is ~108.81 mm accounting for 56.5% of the total annual discharge at the outlet. Furthermore, ~61% of the total annual surface runoff in the Paraguay River Basin flows through the floodplains. Results indicate that the model is able to capture the hydrologic regime in the Paraguay River representing an improvement of SWAT+.

Urban Waterlogging Simulation and Disaster Risk Analysis Using InfoWorks Integrated Catchment Management: A Case Study from the Yushan Lake Area of Ma’anshan City in China

Under the dual pressures of climate change and urbanization, cities in China are experiencing increasingly severe flooding. Using the Yushan Lake area in Ma’anshan City, Anhui Province, as a case study, we employed the InfoWorks Integrated Catchment Management (ICM) hydraulic model to analyze the drainage and flood prevention system of the region and assess the current infrastructure for drainage and flood control. There are 117 pipelines with a return period lower than one year for stormwater and combined sewer systems, accounting for 12.3% of the total number of pipelines. The number of pipelines meeting the one-year but not the three-year return period standard is 700, representing 70.2%. Only 17.5% of the pipelines are capable of handling events exceeding the one-year standard. In simulating a 24 h, 30-year return period rainfall event, the results indicate that floodwater accumulation in the study area is predominantly between 0.15 m and 0.3 m. Most risk areas are classified as low risk, covering an area of 36.398 hectares, followed by medium and high-risk areas, which cover 8.226 hectares and 3.087 hectares, respectively. The Ma’anshan Yushan Lake area has, overall, certain flood control capabilities but faces flood risks during storms with return periods exceeding three years. This research offers valuable insights for improving urban flood management in Ma’anshan City through the development of a stormwater management model for the Yushan Lake area.

Sensitivity of Streamflow to Changing Rainfall and Evapotranspiration in Catchments Across the Nile Basin

This research focuses on the complex dynamics governing the sensitivity of streamflow to variations in rainfall and potential evapotranspiration (PET) within the Nile basin. By employing a hydrological model, our study examines the interrelationships between meteorological variables and hydrological responses across six catchments (Blue Nile, El Diem, Kabalega, Malaba, Mpanga, and Ribb) and explores the intricate balance between rainfall, PET, and streamflow. Nash Sutcliffe Efficiency (NSE) for calibration of the hydrological model ranged from 0.636 (Ribb) to 0.831 (El Diem). For validation, NSE ranged from 0.608 (Ribb) to 0.811 (Blue Nile). With rainfall kept constant while PET was increased by 5%, the streamflows of the Blue Nile, El Diem, Kabalega, Malaba, Mpanga, and Ribb decreased by 7.00, 5.08, 2.49, 4.10, 1.84, and 7.67%, respectively. With the original PET data unchanged, increasing rainfall of the Blue Nile, El Diem, Kabalega, Malaba, Mpanga, and Ribb by 5% led to an increase in streamflow by 9.02, 9.87, 5.38, 4.34, 6.58, and 8.32%, respectively. The research reveals that the rate at which a catchment losing water to the atmosphere (determined by PET) substantially influences its drying rate. Utilizing linear models, we demonstrate that the surplus rainfall available for increasing streamflow (represented by model intercepts) amplifies with higher rainfall intensities. This highlights the pivotal role of rainfall in shaping catchment water balance dynamics. Moreover, our study stresses the varied sensitivities of catchments within the basin to changes in PET and rainfall. Catchments with lower PET exhibit heightened responsiveness to increasing rainfall, accentuating the influence of evaporative demand on streamflow patterns. Conversely, regions with higher PET rates necessitate refined management strategies due to their increased sensitivity to changes in evaporative demand. Understanding the intricate interplay between rainfall, PET, and streamflow is paramount for developing adaptive strategies amidst climate variability. By examining these relationships, our research contributes essential knowledge for sustainable water resource management practices at both the catchment and regional scales, especially in regions susceptible to varying sensitivities of catchments to climatic conditions.

Identifying Soil Erosion-Prone Areas in the Wadi Haly Catchment, Saudi Arabia Using Morphometric Analysis and Watershed Features

Soil erosion has several significant impacts on human and environmental activities that make it an important topic with significant worldwide ramifications. Analyzing morphometric indices provides essential insights into watershed geomorphology, which is key to forecasting and assessing diverse natural hazard dynamics. To ensure effective and sustainable watershed management and resource distribution, it is essential to identify critical catchments or prioritize sub-catchments. In this study, morphometric analysis and prioritization were applied to 15 sub-catchments within the Wadi Haly catchment to identify the one most susceptible to soil erosion. This research focuses on the analysis of 15 sub-catchments within the Wadi Haly catchment in Saudi Arabia, utilizing GIS tools alongside various parameters to guide both short- and long-term catchment management. A combined parameter, developed from several morphometric indices for each sub-catchment, was used to classify the Wadi Haly catchment into three levels of soil erosion risk. The results show that sub-catchments 1, 7, 11, 12, and 13, with areas of 694.1 km², 517.87 km², 677.99 km², 200.39 km², and 326.55 km², respectively, are contributing significantly to erosion in the region. In contrast, sub-catchments 3, 8, 9, 10, and 15 exhibit minimal erosion impact. To mitigate severe erosion, strategies such as contour farming, terracing, the use of filter strikes, as well as various structural or non-structural interventions could be applied.

Promoting Geoheritage in the Aspiring Geopark of Taburno-Camposauro (Southern Apennines, Italy) with Innovative Tools

In the inland areas of Campania (Italy), the Taburno-Camposauro Regional Natural Park covers almost 137 square kilometres. It well represents, in the reliefs that give it its name, the southern segment of the Apennine chain. In fact, the rock outcrops, landscape features and surface and ground water make it possible to reconstruct the geological evolution of this area. Nonetheless, it is possible to understand how the history of man, who has frequented these places since ancient times, has developed by taking advantage of the resources offered by this territory. Among these resources, it is believed that the characteristics of the geological heritage spread throughout the Park can also be an opportunity to attract not only researchers, but also significant tourist flows. To this end, not only has the procedure been initiated to be included in the world network of Geoparks, but efforts have also been made to promote the most representative geological sites using the latest communication tools (e.g., social media). Besides these, numerous initiatives aimed at schools and national tourism agencies were developed. Promotion found particular emphasis with the realisation of an art installation by a well-known author in a water catchment system. In fact, this installation triggered an artistic vein around the beauty of the sites, manifested by videos and photo exhibitions and even forms of entertainment. These events have increased interest in the geological heritage, as evidenced by the increase in visitors observed by a specific analysis of the performance of social media posts, as well as frequent visitors to the geoheritage elements of the Park.

Impacts of agriculture and snow dynamics on catchment water balance in the U.S. and Great Britain

The Budyko water balance is a fundamental concept in hydrology that links aridity to how precipitation is divided between evapotranspiration and streamflow. While the model is powerful, its ability to explain temporal changes and the influence of human activities and climate change is limited. Here we introduce a causal discovery algorithm to explore deviations from the Budyko water balance, attributing them to human interventions such as agricultural activities and snow dynamics. Our analysis of 1342 catchments across the U.S. and Great Britain reveals distinct patterns: in the U.S., snow fraction and irrigation alter the Budyko water balance predominantly through changes in aridity-streamflow relationships, while in Great Britain, deviations are primarily driven by changes in precipitation-streamflow relationships, notable in catchments with high cropland percentage. By integrating causal analysis with the Budyko water balance, we enhance understanding of how human activities and climate dynamics affect water balance, offering insights for water management and sustainability in the Anthropocene.

Multivariate and Spatial Study and Monitoring Strategies of Groundwater Quality for Human Consumption in Corsica

Groundwater, widely used for supplying drinking water to populations, is a vital resource that must be managed sustainably, which requires a thorough understanding of its diverse physico-chemical and bacteriological characteristics. This study, based on a 27-year extraction from the Sise-Eaux database (1993–2020), focused on the island of Corsica (72,000 km2), which is diverse in terms of altitude and slopes and features a strong lithological contrast between crystalline Corsica and metamorphic and sedimentary Corsica. Following logarithmic conditioning of the data (662 water catchments, 2830 samples, and 15 parameters) and distinguishing between spatial and spatiotemporal variances, a principal component analysis was conducted to achieve dimensionality reduction and to identify the processes driving water diversity. In addition, the spatial structure of the parameters was studied. The analysis notably distinguishes a seasonal determinism for bacterial contamination (rain, runoff, bacterial transport, and contamination of catchments) and a more strictly spatial determinism (geographic, lithological, and land use factors). The behavior of each parameter allowed for their classification into seven distinct groups based on their average coordinates on the factorial axes, accounting for 95% of the dataset’s total variance. Several strategies can be considered for the inventory and mapping of groundwater, namely, (1) establishing quality parameter distribution maps, (2) dimensionality reduction through principal component analysis followed by two sub-options: (2a) mapping factorial axes or (2b) establishing a typology of parameters based on their behavior and mapping a representative for each group. The advantages and disadvantages of each of these strategies are discussed.

Combining stable isotopes and spatial stream network modelling to disentangle the roles of hydrological and biogeochemical processes on riverine nitrogen dynamics

Intensive agricultural activities have significantly altered watershed hydrological and biogeochemical processes, resulting in water quality issues and loss of ecosystem functions and biodiversity. A major challenge in effectively mitigating nitrogen (N) loss from agricultural watersheds stems from the heterogeneity of N transformation and transport processes that complicates accurate quantification and modeling of N sources and sinks at the watershed scale. This study utilized stable isotopes of water and nitrate (NO3−) in conjunction with spatial stream network modeling (SSNMs) to explore watershed hydrology, N transformation, and sources within a mesoscale river network in the U.S. Corn Belt (Cannon River Watershed, Minnesota) under contrasting hydrological conditions. The results show that the wet season had elevated riverine NO3− concentration (medium: 8.4 mg N L−1), driven by high watershed wetness conditions that mobilizes NO3− from the near-surface source zone. Furthermore, the strong hydrologic connectivity also reduced the denitrification potential by shortening water travel times. In comparison, the dry season showed lower NO3− concentrations (0.9 mg N L−1) and stronger denitrification NO3− isotope signals. During this period, the decrease in hydrologic connectivity shifted the predominant water source to deep groundwater, with longer water travel time promoting denitrification. After accounting for isotopic fractionations during nitrification and denitrification, we identified fertilizer N as the main NO3− source during the wet season (98.2±1.3%), whereas the dry season showed contributions from diverse sources (64.4±11.9% fertilizer, 26.0±15.8% soil N, and 9.5±6.0% manure and sewage). During the dry season, karst regions with high hydrologic connectivity display increased shallow groundwater inputs, carrying elevated NO3− levels from leaching of applied chemical fertilizers. These findings highlight the importance of integrating drainage water management and N accumulation in groundwater into nutrient management strategies to develop adaptive measures for controlling N pollution in agricultural watersheds.

Modeling the Impacts of Climate Change on Watershed Hydrology Using Climate and Hydrological Models: The Case of the Ziway Lake Watershed, Ethiopian Rift

Modeling the Impacts of Climate Change on Watershed Hydrology Using Climate and Hydrological Models: The Case of the Ziway Lake Watershed, Ethiopian Rift

Local Community Participation Seasonal Flood Disaster in Sidoarjo Regency, East Java

Irrigation in Sidoarjo Regency Drainage System Complex area of carrier channels to irrigation of the drainage (AFVOUR) in the display of water level regulators. High water surface in the channel causes slow flow of rain water catchment to a puddle. Conditions are exacerbated by backwater in the river channel in the area near the coast when the tide, causing floods to not be directly receding. Synergy has a combination of integration of various elements (for example, stakeholders) optimizing something better, legitimacy is considered to equalize perception hoping that actions are carried out in the desired action entity, appropriate according to value norms. Case Study Case data applies certain cases are generalized. Case study data is possible to be used to explore, examine comprehensiveness of a research object. Analysis of data using atlas, The weakness of the government's supervisor handles industrial waste into the River Peraul in Sidoarjo Regency, Urban Sprawl Social Impact Urbanization in big cities, controlling urbanization Increases development using the approach to touch the needs of the community needed Village, equity, spread of village remote development, the level of participation and understanding of the community provides feedback related to the concept of handling routine flood disasters every year. Seasonal flood disaster control in Sidoarjo Regency by involving local communities is an important approach by direct supervision by local communities, counseling on good water management practices, emergency response training, community based infrastructure development, coordinating between the government, local communities, form of concrete participation Local community in Sidoarjo Regency.

Assessing agri-environmental strategies to reduce pesticide concentrations in surface drinking water sources, Coastal Charente River basin, SW France

Most surface water bodies are deteriorating, resulting in health risks and environmental damage. This study aimed to assess the performance of the modeled agri-environmental transition scenarios for restoring freshwater quality within the protection perimeter of strategic surface water drinking water catchments. Realistic agri-environmental scenarios with combined agronomic orientations were tested using a well-calibrated ecohydrological model. Their performance was quantified based on pesticide concentration reductions in freshwater bodies, focusing on temporal and spatial variability, using non-parametric tests. Our results show that it is possible to differentiate cropping mitigation scenarios according to their ability to limit pesticide transfers, taking into account the most influential biogeochemical factors in the catchment, their agronomic orientation, and their progressive implementation. Our study is also applicable to other contexts.

The alien and invasive plant species that may be a future conservation threat to the Lesotho Afro-alpine Drakensberg area

In this study, we documented and compared similarities of the alien plant species richness between South Africa represented by three provinces: Free State (FS), Eastern Cape (EC), and KwaZulu-Natal (KZN), and Lesotho—an important water source area for southern Africa. We tested the prediction that alien plant species in Lesotho are a subset of South Africa’s species partly because of the short geographical distances between the provinces and Lesotho, and environmental similarity. Overall, 7124 records containing 1040 individual alien plant species belonging to 147 families were documented. South Africa had significantly greater alien plant species records than Lesotho. Of 147 plant families, 44 were represented in both countries, and 101 families did not occur in Lesotho. Against the study prediction, the Geraniaceae and Orobanchaceae families occurred in Lesotho but not in three provinces. KwaZulu-Natal had a significantly greater number of species than Lesotho but not the other provinces, and 49% of species in three provinces originated from the Americas (i.e. South and North), Europe, and Asia. A similar pattern was observed in Lesotho. Woody and herbaceous alien plants, habitat transformers, dominated three provinces, while herbaceous species dominated Lesotho. The 62% of 1040 alien species were not listed in the South African national regulations, indicating their negative impacts are also unknown in the study region. Plant nurseries were a dominant species dispersal pathway in South Africa, while home gardens were prominent in Lesotho. We conclude that invasive plant species constitute a future threat to the Lesotho Drakensberg highlands water catchments and recommend prioritising their management and improving cross-border biosecurity between Lesotho and South Africa.

Mapping soil moisture across the UK: assimilating cosmic-ray neutron sensors, remotely sensed indices, rainfall radar and catchment water balance data in a Bayesian hierarchical model

Abstract. Soil moisture is important in many hydrological and ecological processes. However, data sets which are currently available have issues with accuracy and resolution. To translate remotely sensed data to an absolute measure of soil moisture requires mapped estimates of soil hydrological properties and estimates of vegetation properties, and this introduces considerable uncertainty. We present an alternative methodology for producing daily maps of soil moisture over the UK at 2 km resolution (“SMUK”). The method is based on a simple linear statistical model, calibrated with 5 years of daily data from cosmic-ray neutron sensors at ∼ 40 sites across the country. The model is driven by precipitation, humidity, a remotely sensed “soil water index” satellite product and soil porosity. The spatial variation in the parameter describing the soil water retention (and thereby the response to precipitation) was estimated using daily water balance data from ∼ 1200 catchments with good coverage across the country. The model parameters were estimated by Bayesian calibration using a Markov chain–Monte Carlo method, so as to characterise the posterior uncertainty in the parameters and predictions. The approach reduces uncertainty by integrating multiple data sources, all of which have weaknesses but together act as a better constraint on the true soil moisture. The model explains around 70 % of the variance in the daily observations with a root-mean-square error of 0.05 m3 m−3, better than results from more complex process-based models. Given the high resolution of the inputs in time and space, the model can predict the very detailed variation in soil moisture which arises from the sporadic nature of precipitation events, including the small-scale and short-term variations associated with orographic and convective rainfall. Predictions over the period 2016 to 2023 demonstrated realistic patterns following the passage of weather fronts and prolonged droughts. The model has negligible computation time, and inputs and predictions are updated daily, lagging approximately 1 week behind real time.

Integrating material flow analysis into hydrological model for water environment management of large-scale urban-rural mixed catchment

Simultaneous simulation of urban and rural hydrological processes is important for water environment management of mixed land-uses catchments. However, the discharge paths of pollution in the urban drainage system are not described in traditional catchment hydrological models. In this study, an urban-rural water environment (URWE) model is developed through incorporating the material flow analysis (MFA) and the soil and water assessment tool (SWAT) into a general framework. The URWE model is an advancement with respect to traditional hydrological models in terms of simultaneously simulating the urban organized and rural decentralized discharges of pollution. Due to the low data requirement and high computational efficiency of MFA, URWE model is applicable to large-scale catchment with wide urban area. The URWE model is applied to a typical urban-rural mixed catchment, the Dianchi Catchment (China), where the pollution characteristics are analyzed and the pollution control measures are investigated. Results indicate that the URWE model outperforms the conventional SWAT model for both water quantity and quality simulations, with an 8.5 % improvement in average coefficient of determination (R2) and a 67.4 % improvement in average Nash coefficient (NSE). Rural best management practice, rainwater-sewage separation, and storage capacity expansion are identified as the most cost-effective measures for COD, TN, and TP reduction, respectively. Contributions of this study are to improve the accuracy of water environment simulation in urban-rural mixed catchment, as well as to help decision-makers develop synergistic urban-rural water environment management measures.

Spectral Analysis of Hydrological Signals to Estimate Watershed Properties Considering Impacts of Unsaturated Zone

AbstractUnderstanding responses of stream discharge to precipitation in a watershed is important in gaining insights into watershed hydrology and estimating hydraulic parameters. Transfer functions in the spectral domain are commonly used to quantify the relationship between precipitation and discharge, and estimate watershed hydraulic parameters. However, previous models have not adequately accounted for the impact of the unsaturated zone. To address this, we have developed a novel analytical model that considers the effect of the unsaturated zone to obtain transfer functions within watersheds. These transfer functions are derived by the spectral method and verified through numerical simulations. The results indicate that the transfer functions are influenced significantly by the relative hydraulic conductivity exponent αk in the moisture characteristic curve. A higher αk results in a lower transfer function, indicating more robust filtering of hydrological signals. A thicker unsaturated zone results in lower transfer functions at higher frequencies. The traditional transfer functions, which neglect the retention capacity of the unsaturated zone, tend to overestimate hydrological responses at high frequencies. Our transfer functions agree well with integrated watershed‐scale flow models and are also applied to observed data from four watersheds in Iowa, providing reasonable estimates for the hydraulic parameters. This study contributes to a deeper understanding of watershed behavior and offers an enhanced tool for estimating hydraulic parameters with practical applications.