Hydrologic Modeling for Sustainable Water Resources Management in Urbanized Karst Areas

Nonlinear hydrological time series modeling to forecast river level dynamics in the Rio Negro Uruguay basin

Floods significantly impact the well-being and development of communities. Hence, understanding their causes and establishing methodologies for risk prevention is a critical challenge for effective warning systems. Complex systems such as hydrological basins are modeled through hydrological models that have been utilized to understand water recharge of aquifers, available volume of dams, and floods in diverse regions. Acquiring real-time hydrometeorological data from basins and rivers is vital for establishing data-driven-based models as tools for the prediction of river-level dynamics and for understanding its nonlinear behavior. This paper introduces a hydrological model based on a multilayer perceptron neural network as a useful tool for time series modeling and forecasting river levels in three stations of the Rio Negro basin in Uruguay. Daily time series of river levels and rainfall serve as the input data for the model. The assessment of the models is based on metrics such as the Nash-Sutcliffe coefficient, the root mean square error, percent bias, and volumetric efficiency. The outputs exhibit varying model performance and accuracy during the prediction period across different sub-basin scales, revealing the neural network's ability to learn river dynamics. Lagged time series analysis demonstrates the potential for chaos in river-level time series over extended time periods, mainly when predicting dam-related scenarios, which shows physical connections between the dynamical system and the data-based model such as the evolution of the system over time.

Groundwater security indicators and their drivers: An assessment made in a region of tropical climate (Paraopeba River basin, Brazil)

Groundwater helps overcoming periods of drought buffering their effects on water supply to people, natural ecosystems and the economy. Following the latest Conference of the Parties (COP27), groundwater research gained renewed impulse because the Parties committed themselves to invest on environmental dimensions of water security related with aquifer characterization and protection. In that context, the purpose of this study was to help providing an integrated assessment to some fundamental issues about groundwater security, summarized as the three "how"s: how much, how ready and for how long can groundwater be delivered from watersheds? A complementary goal was to identify and quantify the role of watershed characteristics controlling these "how"s. The methodology combined hydrologic modeling and GIS and the results for the test site (Paraopeba River basin, Brazil) were: (1) the studied river tributaries mostly drain regolith aquifers with short hydrologic turnover times (1.3-23.7 yr) and small aquifer mobile storages (0.1-1.3 m), but high specific yields (0.2-8.2 m/yr), being generally prone to hydrologic droughts; (2) the specific discharge is primarily elevation controlled (via precipitation increases with altitude), but relates positively with drainage density as well; (3) the mobile storage in the Quadrilátero-Ferrífero mountain is larger than elsewhere, being influenced by a local geomorphologic setting (higher coverage with concave hillslopes); (4) the groundwater contribution to streamflow discharge is high (> 50 %, on average), being improved with the coverage of argisols; (5) vulnerability to droughts could be alleviated through expansion of water-retention infrastructure in specific regions, as well as through land use conversions targeting reduced evapotranspiration or sustainable land management of argisol and concave surface landscapes. Although applied to a specific catchment, our results stand on a site-independent methodological framework. Thus, the understanding about groundwater security gained with this study can be inspiring to other workers dealing with tropical climate landscapes.

Assessment of the Streamflow and Evapotranspiration at Wabiga Juba Basin Using a Water Evaluation and Planning (WEAP) Model

Rapid population growth, industrialization, and agricultural activities have impacted water resources in the arid and semi-arid areas of Somalia. The Lower Juba region in Somalia has been the most affected region. Therefore, an analysis of the hydrological patterns is essential. This paper assesses streamflow and evapotranspiration in the Wabiga Juba basin in Somalia using a hydrological simulation model, namely, the water evaluation and planning (WEAP) system via the soil moisture method. The datasets included 53 (average precipitation) and 13 (streamflow) year periods from two meteorological stations. The estimated values for potential evapotranspiration (11,921.98 to 20,775.39 MCM) were higher than the actual evapotranspiration (4904.10 to 8242.72 MCM) by 50 to 79.5%, respectively. The annual streamflow in Juba Dolow and runoff proportion of the Wabiga Juba River was estimated to be 10% of the annual precipitation. Most of the surface runoff occurred in April (47%), May (31%), October (5%), and November (14%). The streamflow variation responded to the pattern of precipitation. The model performance achieved a Nash–Sutcliffe model efficiency (NSE) coefficient of 0.71, coefficient of determination (R2) of 0.91, and percent bias (PBIAS) of 14%. The WEAP model of the Wabiga Juba basin is a baseline study for water resource management in Somalia to mitigate water shortage impacts due to limited water resources.

The COP27 screened through the lens of global water security

Water security is an expression of resilience. In the recent past, scientists and public organizations have built considerable work around this concept launched in 2013 by the United Nations as "the capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-borne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability". In the 27th Conference of the Parties (COP27), held in Sharm El-Sheikh (Egypt) in last November, water security was considered a priority in the climate agenda, especially in the adaption and loss and damage axes. This discussion paper represents the authors' opinion about how the conference coped with water security and what challenges remain to attend. As discussion paper, it had the purpose to stimulate further discussion in a broader scientific forum.

Water Yield Alteration in Thailand’s Pak Phanang Basin Due to Impacts of Climate and Land-Use Changes

Climate and land-use change are important factors in the hydrological process. Climatic and anthropic changes have played a crucial role in surface runoff changes. The objective of this research was to apply land-use change and future climate change to predict runoff change in the Pak Phanang River Basin. The Cellular Automata (CA)-Markov model was used to predict the land-use change, while the climate data from 2025 to 2085 under RPC2.6, RPC4.5, and RPC8.5 were generated using the MarkSim model. Additionally, the Soil and Water Assessment Tool (SWAT) combined land-use change and the generated meteorological data to predict the runoff change in the study area. The results showed that the annual runoff in the area would increase in the upcoming year, which would affect the production of field crops in the lowland area. Therefore, a good water drainage system is required for the coming years. Since the runoff would be about 50% reduced in the middle and late 21st century, an agroforestry system is also suggested for water capturing and reducing soil evaporation. Moreover, the runoff change’s overall impact was related to GHG emissions. This finding will be useful for the authorities to determine policies and plans for climate change adaptation in the Malay Peninsula.

Development of Rainfall-Runoff Models for Sustainable Stormwater Management in Urbanized Catchments

Modelling of stormwater networks and the related object (combined sewer overflows, diversion chambers, retention tanks) is a complex task requiring colleting of data with appropriate time and spatial resolution as well as application of adequate models. Often there is a need to find balance between the costs of conducting measurement (period, resolution) and the uncertainty of the model results. This paper presents an overview of simulation tools for sewerage networks modelling, related objects, as well as low-impact development (LID) systems in relation to the hydrodynamic and statistical models. Consecutive stages of data collection, sources of data uncertainty, limitations resulting from the adopted measurement methodology, as well as their influence on the simulation results and possible decision-making using the developed hydrodynamic or statistical model, are discussed. Attention is drawn to the optimization methods enabling reduction in the uncertainty of statistical models. The methods enabling the analysis of model uncertainty, as well as evaluation of its influence on the calculation results pertaining to stormwater hydrographs, retention tank capacity and combined sewers overflows, are also discussed. This is a very important aspect in terms of optimizing construction works in the sewerage network and designing their appropriate dimensions to achieve the assumed hydraulic effects.

Watersheds, Anthropogenic Activities and the Role of Adaptation to Environmental Impacts

Runoff has shaped the Earth into watersheds, and humans have appropriated many of them [...]

Identification and Estimation of Solute Storage and Release in Karst Water Systems, South China

Solute storage and release in groundwater are key processes in solute transport for groundwater remediation and protection. In karst areas where concentrated recharge conditions exist, pollution incidents can easily occur in springs that are hydraulically connected to densely inhabited karst depressions. The intrinsic heterogeneity common in karst media makes modeling solute transport very difficult with great uncertainty. Meanwhile, it is noteworthy that solute storage and release within subsurface conduits and fissures exhibit strong controlling function on pollutant attenuation during underground floods. Consequently, in this paper, we identified and estimated the solute storage and release processes in karst water systems under concentrated recharge conditions. The methodology uses the advection–dispersion method and field tracer tests to characterize solute transport in different flow paths. Two solute transport pathways were established (i.e., linear pathway (direct transport through karst conduits) and dynamic pathway (flow through fissures)). Advection–dispersion equations were used to fit the breakthrough curves in conduit flow, while the volume of solute storage in fissures were calculated by segmenting the best fitting curves from the total breakthrough curves. The results show that, greater recharge flow or stronger dynamic conditions leads to lower solute storage rate, with the storage rate values less than 10% at high water level conditions. In addition, longer residence time was recorded for solute exchange between conduits and fissures at the low water level condition, thereby contributing to a higher solute storage rate of 26% in the dynamic pathway.

Assessment of Future Water Demand and Supply under IPCC Climate Change and Socio-Economic Scenarios, Using a Combination of Models in Ourika Watershed, High Atlas, Morocco

Climate change will affect the water resources system, on global and regional levels. Over the past thirty years, the High Atlas Mountains in Morocco have experienced severe droughts, which causes a decrease in water supply that affects both agriculture and the urban water system. In this paper, we assess the impact of climate change and socio-economic activities on water supply and demand in the Ourika watershed (High Atlas of Morocco), then we evaluate the efficiency and sustainability of regional adaptation strategies for water supply management. For this, we simulate and analyze the future water situation using the statistical downscaling model (SDSM) and the water assessment and planning tool (WEAP). After the model’s calibration and validation, the precipitation, minimum (Tmin) and maximum (Tmax) temperatures, water demand and unmet water demand were projected for 2100 horizon, using different climate change scenarios. The results revealed that the model’s performance, calibration and validation were found to be satisfactory. The analysis shows that the mean precipitation will decrease by 49.25% and 34.61% by 2100, under A2 and B2 emission scenarios of the Intergovernmental Panel on Climate Change (IPCC). The projected mean Tmax and Tmin will be warmer than the baseline period, with Tmax increasing by 4.2 °C (A2) and 3.6 °C (B2), and Tmin by 3.5 °C (A2) and 2.9 °C (B2) by 2100. The results also show that water demand and the unmet water demand will increase in all scenarios, the pressure on water resources will increase, leading to water scarcity. The results reveal that, under the influence of climate change, future unmet water demand is expected to reach 64 million cubic meters (MCM) by 2100. The results demonstrate that the assessments of the proposed adaptation strategies are effective, but not sufficient to ensure water sustainability for the Ourika watershed.

Application of Geophysical and Hydrogeochemical Methods to the Protection of Drinking Groundwater in Karst Regions

To provide theoretical support for the protection of centralized drinking groundwater sources in karst areas, it is necessary to accurately identify the development of karst conduits and analyze the differences in hydrogeochemical characteristics of different karst systems. This provides a scientific basis for the accurate designation of risk zones that may cause drinking groundwater pollution. In this study, a geophysical survey, hydrogeological chemical process analysis and optimized fuzzy cluster analysis were used to gradually improve the understanding of karst water systems. AMT and HDR methods were used to calibrate the resistivity around the water-filling karst conduits, which ranged from 39 to 100 Ω•m. A total of seven karst systems were identified, including four karst systems in the north of the study area, one karst system in the west and two karst systems in the south. Analysis of the hydrochemical data showed that HCO3-Ca and HCO3-Mg-Ca types accounted for 90% of all samples. The δD and δ18O values of their main conduits were -51.70‱ to -38.30‱ and -7.99‱ to -5.96‱, respectively. The optimized fuzzy clustering analysis method based on the weight of variables assigned by AHP more accurately verified karst water systems. Based on these findings, the drinking groundwater source risk zone was designated with an area of 33.90 km2, accounting for 34.5% of the study area. This study effectively improved the rationality and accuracy of the designation of drinking groundwater source risk zones in karst areas, and provided a scientific basis for the identification of karst water systems and decision-making of drinking groundwater source protection in karst areas.