Journal of Hydrology-Regional Studies最新文献

Study region

Alpine shrubland on the northeastern Qinghai-Tibetan Plateau.

Study focus

Water provision ability is a pivotal ecological service of high-altitude alpine regions and is controlled by precipitation, evapotranspiration (ET), and soil water storage whereas the underlying ecohydrological processes remain highly unquantified. Here, we investigated continuous 19-year flux measurements to quantify the temporal patterns of ET and water budget (precipitation minus ET, P−ET), as well as 0-20 cm soil water storage change (ΔSWS).

New hydrological insights for the region

At a monthly scale, ET peaked in July (96.7 ± 26.4 mm, Mean ± S.D.) and averaged 41.7 ± 31.9 mm, whose variations were determined by the slope of the saturation vapor pressure curve at air temperature, air and soil temperatures, regardless of vegetation growth stage. P−ET averaged 18.3 ± 26.3 mm in August and September while stayed deficit during the other months. The variations in P−ET were controlled by precipitation in the May-October growing season whereas by ET in the non-growing season from November to April. ΔSWS peaked in May (28.8 ± 11.2 mm) and September (3.0 ± 2.7 mm) and almost accumulated to zero over the whole season. At annual scales, none of ET, P−ET, and ΔSWS changed significantly. ET averaged 512.2 ± 68.4 mm and exceeded precipitation (459.1 ± 58.4 mm), likely due to the lateral flow supply of uphill locations. The variations in ET were regulated directly by bulk canopy resistance and indirectly by net radiation. P−ET averaged −53.2 ± 95.4 mm and demonstrated a clear water deficit (−51.6 ± 21.0 mm) during the non-growing season. The variations of P−ET were driven jointly by precipitation and ET, with opposite but equivalent effects. The dominance of thermal conditions and energy availability on ET variability manifested an energy-limited feature of water loss in the alpine shrubland. The temporal patterns in P−ET elucidated that the alpine shrubland plays the water retention rather than water provision function through transforming variable precipitation input into stable ET loss.

Study region

A reach of the Nile River located between Naga Hammadi barrage and Asyut barrage, Egypt

Study focus

An accurate representation of hydrodynamics of an important water source helps cope with expected future climate changes, pollution incidents and water quality problems. Here, a comparison between HEC-RAS 1D and TELEMAC-2D model was conducted by identifying different Manning coefficients. Moreover, an automatic calibration using Dual-Annealing optimization method was applied for first time to calibrate the model with non-uniform Manning coefficients. The transport of tracer (pollution) was simulated by computing tracer residence times. Pollution transport scenarios were discussed to draw a picture of pollution incidents which will continue to happen in the future. An equation indicating the relation between flow discharge and residence time was derived to hurriedly help decision makers in water management during sudden pollution incidents.

New hydrological insights for the region

A model with spatially variable Manning coefficients using TELEMAC-2D was set up and calibrated achieving good accuracyies with average errors of approximately 4 cm and 7 cm between field and simulated water levels for two different discharge scenarios. Moreover, an equation for relation between flow discharge and residence time was derived producing a strong correlation coefficient of 0.95. This study, integrating advanced hydrodynamic models and automatic calibration techniques, provides a robust framework for assessing and managing water resource challenges under varying flow conditions.

Study region

Afghanistan, Central Asia.

Study focus

In this study, we evaluated the terrestrial water storage dynamics in Afghanistan and its five major river basins using the terrestrial water storage anomalies (TWSA) from three Gravity Recovery and Climate Experiment (GRACE) mascons observations from JPL, CSR, and GSFC processing centers, and the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System – Central Asia (FLDAS-CA) simulation.

New hydrological insights for the regions

Since 2008, due to intense and prolonged drought conditions and groundwater overexploitation, TWS in Afghanistan has been decreasing at an alarming rate. The average slopes of the TWSA trend in Afghanistan for the GRACE period (2003–2016) of the three products range between − 3.6 to − 4.8 mm/year. The decrease in TWS is further exacerbated during the GRACE-FO period (2019–2022), ranging between − 20.4 to − 30 mm/year. Because groundwater is heavily relied on in the country but human-induced change (i.e., groundwater extraction) is not simulated in FLDAS-CA, a significant difference could be observed between GRACE observations and FLDAS-CA results, especially following after each severe drought event (e.g., 2008, 2018) when substantial groundwater extraction occurred. The assimilation of GRACE observations into the FLDAS-CA framework will undoubtedly have a positive impact for decision-makers and local stakeholders in preparing and mitigating the impacts of drought and groundwater overexploitation in Afghanistan and Central Asia.

Study region

Tropical watershed in the Colombian Andes, the Chico River (CR) watershed.

Study focus

Hydrological models are widely used to project the impacts of LULC (Land Use/Land Cover) change on water budget. However, their ability to produce reliable predictions depends on how accurately they represent the role of vegetation in the watershed’s water balance. We analyze how different representations of Leaf Area Index (LAI) affect streamflow responses to LULC change using the Soil and Water Assessment Tool (SWAT) model. We also examine streamflow response to 100 % pasture cover (PAS), 100 % forest cover (FOR), and a control scenario using the original SWAT model, SWAT-T, and a proposed new variant (SWAT-Tb), which improves LAI bimodal representation for tropical regions.

New hydrological insights for the region

SWAT-T and SWAT-Tb reproduce observed LAI and streamflow in the CR watershed. However, SWAT-T restricts LAI simulation to unimodal seasonality, while the original SWAT reproduces streamflow but not LAI seasonality. Results using SWAT-T (unimodal LAI) and SWAT-Tb (constant and bimodal LAI) show streamflow increases during the dry seasons for the FOR scenario and decreases for the PAS scenario. Conversely, the original SWAT, with its default LAI representation, tends to underestimate and overestimate streamflow changes in the FOR and PAS scenarios, respectively. Our results highlight that an unrealistic LAI representation can mislead LULC change impact assessments on streamflow in the tropical Andes.

Acacia mearnsii and Eucalyptus dunnii plantations play an important role in the South African economy as a source for a variety of wood products. However, these species are commonly associated with high evapotranspiration (ET) which may cause streamflow reduction, affecting downstream water users who are reliant on the stream for survival. The potential future increase in exotic plantations worldwide necessitates understanding the impact of these different species on the water balance, hence the streamflow. At the Two Streams research catchment in South Africa, intense hydrological observations (streamflow, ET and weather) have been conducted on A. mearnsii for almost two decades. In 2018, the catchment was clear-felled with subsequent replanting of E. dunnii and hydrological measurements continued. This provided an opportunity to present observations of the surface water balance of the catchment. However, gaps in the data at various times prevented a compilation of a continuous hydrological record. Therefore, three window periods, with complete records of streamflow, ET and precipitation, and with similar weather conditions, were compared. Only the interception loss (I_l) was estimated using the Von Hoyningen-Huene method. First window, A. mearnsii trees were three years old (Amear₃), second window, A. mearnsii trees were seven years old (Amear₇) and the third window, E. dunnii trees were three years old (Edun₃). Results indicated a negative catchment surface water balance for all window periods. During the Amear₇ window period, the I_l was highest compared to the young crops, which reduced effective precipitation, in turn contributing to the lowest measured streamflow. The negative surface water balance and high ET, suggests that trees were accessing water not quantified in the surface water balance. Crops of all three window periods were found to have the potential to significantly reduce the streamflow, which may in turn affect downstream water users. Further research using isotopes to trace the sources of water used by trees in the system is suggested.

Study region

South-east Mediterranean France

Study focus

Urbanisation and climate change are producing unprecedented flood risks. Urbanisation increases storm peak discharge and flooded area. Building in the flood plain exposes more people and infrastructure to floods. This study examines the impact of urbanisation over 3 decades (1988/90–2020) on flood risk in SE France. Building footprint layers were used to quantify urban growth, and peak discharge and flooded area were modeled for 3 12-hr rainfall events: 80 mm, 140 mm, and 200 mm. Building growth ranged from 28 % to 65 %. Total imperviousness grew at a rate that was equal to or greater than built area. The relative increase in peak discharge was greatest for the 80-mm event (+12.2 %) and diminished to its lowest value for the 200-mm event (+2.4 %).

New hydrological insights for the region

Flooded area increased proportionately to changes in peak discharge, but mean growth in flooded building footprint area was almost 43 times greater than growth in flooded area. New buildings within the flooded perimeter contributed more to flood risk than changes in peak discharge and flooded area. Planning legislation limited growth close to channels, but flood risk grew rapidly beyond in less restricted areas. Building footprint data provide an accurate approach to mapping changes in flood risk with urbanisation.

Study region

karst rocky desertification area, China

Study focus

The rocksoil interface, where exposed bedrock is in abrupt contact with the soil, is prevalent in rocky desertification areas. As a constraining boundary condition of soils, drying shrinkage cracks are easily developed at the rocksoil interface of outcrops with weak or un-weathered bedrock, but the shrinkage crack development under these conditions is still unknown, which seriously restricts a profound understanding of the hydrological processes on karst slopes with exposed bedrocks. This study aims to quantify the geometric morphological characteristics of these shrinkage cracks and the block areas cut by the crack network during the crack development, as well as to explore the development of drying shrinkage cracks at the rocksoil interface of outcrops.

New hydrological insights

When the soil moisture content was between 24.1 % and 28.6 %, shrinkage cracks at the rocksoil interface (CRSI) first formed along the border between rocks and soils and then at the soil surface perpendicular to the former, most of the cracks intersected vertically in shapes of "T" or "+". The geometric parameters of shrinkage cracks initially increased before stabilizing and reached a stabilization stage as soon as the moisture content decreased. However, all of them finally shrank slightly in the later stages of soil water loss in thicker soils. Soil thickness was not a crucial factor affecting the CRSI formation. The CRSI were 1.2 times wider than all other cracks, while being infrequent and making up just 40 % of the total length and area of all cracks. As a result, the CRSI may grow into a key pathway for the establishment of preferred flow at the rocksoil interface, which should be paid attention in the hydrological processes in the karst rocky desertification region.

Groundwater potential in Morocco’s Souss-Massa mountainous basin (SMMB) is being identified using geospatial tools and geological data. We deployed four mathematical models, namely Data-Driven Multi-index Overlay (DM_IO), Geometric Average (G_A), Support Vector Machine (SVM), and Logistic Regression (LR), to establish data-driven patterns among the nine influencing factors, primarily drainage density, permeability, slope, distance to rivers, elevation, lineament density, distance to lineaments, intersection node density, and rainfall. Based on the Concentration-Area (C-A) fractal approach, the findings of the four models were developed and classified into five levels of potentiality ranging from very low to very high. The regions designated as having high and very high potentialities for the DM_IO, G_A, SVM, and LR models, respectively, account for 22.44 %, 9.80 %, 19.36 %, and 26.77 % of the overall basin. We validated the models by calculating each model's area under the ROC curve (AUC). The estimated AUC values are more than 70 %, suggesting the model performs well. The four models' performance was compared, revealing that the SVM model outperforms the others. Gravimetric data shows that possible groundwater zones closely coincide with gravimetric lineaments. The findings of this study can provide valuable insights to decision-makers, allowing them to improve decision-making processes and develop holistic groundwater resource management in the Souss-Massa mountainous basin (SMMB).

Study area

The western and eastern flanks of Ethiopia's Awash and Abay Basins, respectively.

Study focus

Identifying recharge zones of the main aquifers in the Upper Awash Basin, which are water resources targeted for long-term sustainable use. In this work, lithohydrostratigraphic concepts with fracture density, hydrogeochemical and stable isotopic insights were applied using information from 94 water-supply wells, 188 geoelectrical resistivity, 124 hydrochemistry, and 81 stable isotopic data sets.

New hydrogeological insights of the area

The results illustrate that recharge of superficial deposits and Rift basalt aquifers is from modern precipitation and from nearby streams/rivers through fractures, which is exemplified by mixed CaHCO₃ or CaMgHCO₃ water types of low TDS (<200 mg/l), high Ca/Na ratio (>5), low RA (<2.0), enriched isotopic signature, and high deuterium excess (13.3). Seepage from the overlying aquifers, as well as direct precipitation in locations where the unit is exposed, form the mechanisms of recharge for fractured ignimbrite aquifer. The highland and transition areas are dominantly the recharge areas for the regional scoriaceous basalt aquifer. These areas have high fracture density (0.96<FD<3.0 km/km²), mineralized NaHCO₃ water type, high TDS (>468 mg/l), low Ca/Na ratio (<1), high RA (>2.0), highly depleted isotopic signals, and low deuterium excess (<11) relative to the Local Meteoric Water Line. The results also reveal groundwater flux from the adjacent eastern flank of Abay Basin.

Study region

Prahova river basin located in the central-southern region of Romania.

Study focus

This study aims to assess the susceptibility to flooding by using state-of-the-art machine learning and optimization procedures. To achieve this goal, we employed ten flood-related variables as independent variables in our machine learning models. These variables include slope angle, convergence index, distance from the river, elevation, plan curvature, hydrological soil group, lithology, topographic wetness index, rainfall, and land use. We used 158 flood locations as dependent variables in the training of four hybrid models: Deep Learning Neural Network-Statistical Index (DLNN-SI), Particle Swarm Optimization-Deep Learning Neural Network-Statistical Index (PSO-DLNN-SI), Support Vector Machine-Statistical Index (SVM-SI), and Particle Swarm Optimization-Support Vector Machine-Statistical Index (PSO-SVM-SI). Utilizing the Statistical Index method, we calculated coefficients for each flood predictor class or category.

New hydrological insights for the region

The PSO-DLNN-SI model demonstrated the best performance, achieving an AUC-ROC curve of 0.952. It's worth noting that the application of the PSO algorithm significantly enhanced the model's performance. Additionally, it's crucial to highlight that approximately 25 % of the study region exhibits a high to very high susceptibility to flood events. Taking into account the very precise results of the models applied in the present study, we can state that from a hydrological point of view, the current research contributes to a better understanding of the intensity with which floods can affect the different areas of the Prahova river basin.