Journal of Hydrology-Regional Studies最新文献

Study region

The southwestern coast of Taiwan.

Study focus

By employing sea-level rise (SLR) projections from the Sixth Assessment Report, we assess the future high tide flooding (HTF) and the resulting inundation extents and evaluate the impacts on populations and economic losses.

New hydrological insights for the region

Under the low-emissions scenario, SLR-induced minor HTF days, i.e., 0.55 m above the mean higher high water (MHHW) are projected to exceed 300 annually by 2100; moderate HTF (0.85 m above the MHHW) events are expected to occur daily in the high-emissions scenario by 2090; major HTF (1.2 m above the MHHW) events were projected to occur in 2070, regardless of the emission scenario considered; regarding the extent of inundation, the projected HTF events would lead to a flooded area ranging from 30 to 600 km2. The impact on the present population ranged from 41,000 to 490,000 individuals. The upper limit of total economic losses based on current land use resulting from HTF was anticipated to range from 3.25 million US dollars to 35.31 million US dollars across the low-, medium-, and high-emission scenarios. The at-risk population decreased from 520,000 in 2008–490,000 in 2022, representing a decline of 5.8 % over 15 years in this coastal region.

Study region

Sanjiang Plain, China

Study focus

The characterization of groundwater drought is inadequate, particularly in terms of the differences in the drought propagation dynamics between cropland and other regions. In this study, we identified groundwater drought events and characteristics in the Sanjiang Plain, using the standardized groundwater drought index (SGDI); we also quantified the mechanism of dynamic factors influencing drought propagation characteristics based on the geodetector method and wavelet coherence analysis and discussed the correlation between the NDVI and SGDI.

New Hydrological Insights for the Region: The drought propagation time was shorter during summer and longer during spring and autumn in irrigated areas than in nonirrigated areas. The groundwater system exhibited greater resistance to drought during summer, and spatially nonirrigated area was more vulnerable to meteorological drought. The factor that best explained the variation in propagation time and threshold differed across seasons. A significant correlation time-frequency domain existed between all the factors and SGDI in nonirrigated area, with the SGDI exhibiting the fastest response to soil moisture. The relationship between the SGDI and factors was characterized by a discontinuous response of less than 8 months and a continuous response of more than 30 months. The correlations between the SGDI and NDVI in irrigated and nonirrigated area exhibit different changes due to groundwater exploitation and differences in plant physiology between artificial crops and natural vegetation.

Study region

Ethiopian and Kenyan Rift Valley (EKRV)

Study focus

The morphological changes in EKRV lakes exemplify the complex interplay between human activities and natural systems. This review investigates the spatiotemporal water level fluctuation in EKRV lakes and its causes, highlighting the gaps in existing research on the natural and anthropogenic factors. We employed a meta-analysis of the literature establishing a database of 362 documents consisting of peer-reviewed journal articles, conference proceedings, theses, and book chapters. These documents were collected from online sources and supplied by authors upon request. Of these 362 documents, 236 were critically assessed using systematic review procedures.

New hydrological insights for the region

The review reveals contrasting morphological changes, with the Kenyan Rift Lakes expanding and the Ethiopian Rift Lakes either shrinking or expanding. Endorheic lakes suffered the most fluctuations due to the extensive loss of forest and woodlands in their watersheds. The research emphasizes the necessity of managing resources holistically, acknowledging the interdependence of upstream and downstream ecosystems and the significance of cross-border cooperation. The influence of climate change and the consequences of lake water level fluctuations on water quality and fragile natural resources in the Rift Valley urges interdisciplinary research integrating natural and social sciences to safeguard the invaluable ecosystem services provided by lakes sustainably.

Study region

30 catchments in Morocco.

Study focus

We assessed the KGE performance of eight monthly lumped hydrological models forced by ground-based rainfall observations. We then examined how the performance relates to model complexity and structure, applied exploratory correlation analysis to identify the catchment features (over 200 features were considered) most significantly related to model performance, and investigated how these models respond to three rainfall forcings (ERA5, CHIRPS, and PERSIANN-CDR).

New hydrological insights for the region

The findings indicate that no hydrological model outperformed (or underperformed) consistently across all the catchments and that model performance depends more on model structure and hydro-climatic characteristics, particularly those related to calibration and calibration-validation data difference, than on model complexity and non-hydro-climatic features. The linearity between rainfall and runoff was the primary feature influencing model performance. Additionally, besides the expected improvement of model performance when forced with richer rainfall and runoff calibration data in terms of wet and dry years, our results show that this holds true even if the calibration data is only relatively richer than the validation data and that dry periods are more beneficial to model performance than wet periods. Lastly, all the models responded similarly to the different rainfall inputs; each model performed better when using ERA5 than when using CHIRPS and underperformed when using PERSIANN-CDR. The metric that best explained this similarity was the Pearson correlation coefficient between the precipitation products and observed runoff.

Study region

The Heihe River source area in the Northeastern Qinghai-Tibetan Plateau, China.

Study focus

Soil evaporation, which is a key process in soil water loss, is influenced by various environmental factors. However, the identification of its main drivers on a large scale in alpine mountains remains challenging due to sampling constraints. This study examined the spatial distribution of soil evaporation and control factors during the growing season in the Heihe River source area.

New hydrological insights

The results indicated that soil evaporation, represented by lc-excess values, gradually increased from southeast to northwest, and then decreased, reaching a depth of 50 cm below the surface. Although the normalized difference vegetation index explained 54 % of the spatial variation in soil evaporation, the interaction between land surface temperature and soil water content (SWC) provided a more robust explanation. The soil evaporation losses exhibited the following pattern: cropland > grassland > forest land > shrubland. In forest land and shrubland, SWC and precipitation explained 68 % and 73.3 % of the spatial variations in soil evaporation, respectively. Grassland mainly relied on temperature and SWC, with 49.33 % of unexplained spatial variability by environmental factors. Meanwhile, the aridity index and aspect explained 45 % and 44.6 % of the spatial variations in cropland. These findings provided invaluable information for advancing our understanding of the ecohydrological processes in alpine mountains.

Study region

Agricultural Irrigation and Drainage system - Ulansuhai Lake Continuum, located in the Hetao Irrigation District, Inner Mongolia, China.

Study focus

In this study, carbon isotope tracing technology was applied to analyze the sources and migration-transformation characteristics of Dissolved Organic Carbon (DOC) and Dissolved Inorganic Carbon (DIC) in the continuous system of the agricultural irrigation and drainage system - Ulansuhai Lake in the Hetao Irrigation Area of Inner Mongolia during typical irrigation periods.

New hydrological insights for the region

During typical irrigation periods, DOC and DIC increase simultaneously with the increase in salinity, and dissolved carbon dioxide in the irrigation and drainage channels escapes. The main sources of DOC in farmland drainage water are terrestrial C3 plants (94.00 %) and plankton (6.00 %). The primary sources of DOC in the lake are farmland drainage (98.19 %) and macroaquatic plants (1.81 %). The main sources of DIC in farmland drainage water are irrigation water from the Yellow River (64.73 %) and the equilibrium dissolution process between carbonates and soil CO₂ (35.27 %); while the primary sources of DIC in the lake are farmland drainage (93.10 %) and air-water exchange (6.90 %). Crop types in the irrigated area, soil salinization, rock weathering, metabolic processes, and the hydrological connectivity induced by irrigation from the Yellow River jointly control the sources, migration, and transformation of carbon within the continuum.

Study Region

A humid subtropical basin, Poyang Lake Basin, China.

Study focus

Drought-flood alternation (DFA) is sub-seasonal precipitation anomaly, which has more serious impact on agricultural production, ecology and environment than a single drought or flood event. The study evaluated the suitability of high-resolution satellite-based precipitation product for identifying the DFA event and quantified the spatiotemporal patterns of the frequencies and intensities of DFA at various time scales.

New hydrological insights for the region

The Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG) product could effectively identify the DFA events at 1-month scale, with high consistency with the results based on traditional rain-gauge data, however, its performance was not very satisfactory at 3-month and 6-month scales. Drought-to-Flood (DTF) events usually occurred from March to June, while Flood-to-Drought (FTD) events mainly occurred during from July to September. Frequencies and intensities of both DTF and FTD exhibited significant spatial heterogeneity. The lake area was mainly affected by DTF events, and the Ganjiang sub-catchment was mainly affected by FTD events. Especially, the southern part of the basin was a high-risk area affected by DFA, with higher frequencies of both severe DTF and FTD events. Furthermore, although the total area affected by DFA events showed a long-term decreasing trend from 2000 to 2019, the area affected by severe DTF and FTD events was gradually expanding in Poyang Lake basin.

Study region

Global and 28 large river basins

Study focus

Actual evapotranspiration (ET_a) plays a key role in the redistribution of water, carbon and energy. The emergence of many ET_a products has made uncertainty assessment increasingly important. The FLUXNET2015 dataset and 28 large watershed water balance datasets were used in this study. The monthly scale products of the ERA5-Land reanalysis data (ERA5), Global Land Data Assimilation System (GLDAS), Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA) and Penman-Monteith-Leuning Model Version 2 (PML) terrestrial evapotranspiration models were evaluated from 2001 to 2017. The differences in composition (vegetation transpiration (T), soil evaporation (E_s), canopy interception loss (E_i) and other components (open water and ice and snow sublimation) (E_o)) and vegetation among the four ET_a products were compared.

New Hydrological Insights for the Region: At the site scale, the ERA5 and MERRA products significantly outperformed the GLDAS and PML products, with the latter exhibiting poorer reliability in site validation. The PML product's basin-scale water balance KGE metric overall outperformed those of the ERA5, GLDAS, and MERRA products, with KGE > 0 in 23 basins. The use of basin-scale data mitigates the impact of local outliers on the simulation results, leading to KGE validation metrics at the basin scale that are overall superior to those obtained from site-scale validation. There were large errors in the estimates of T and E_s in the ERA5 product, related to the overestimation of E_s and underestimation of T. The boundary between sea and land (used to divide marine evapotranspiration and land evapotranspiration) was unclear in the PML products. E_o/ET_a was overestimated, and there were clearly high values at the land margin (E_o peaks as high as 3803 mm/yr). The difference in evapotranspiration components had a considerable influence on the uncertainty of ET_a. The vegetation types in the 4 ET_a products for DBF***, EBF***, ENF***, MF***, GRA***, and CRO*** all exhibited significant differences at the P<0.001 level. This study contributes to product uncertainty analysis and the determination of ways to improve ET_a products.

Study area

Iran.

Study focus

Hamedan-Bahar plain is one of the important plains in the west of Iran, which is facing a shortage of water resources and excessive extraction of groundwater resources. The purpose of this article is to identify and evaluate the status of sustainability governance indicators using the knowledge of local experts, which can be an effective step towards the sustainable management of groundwater resources. In this paper, we apply Ostrom’s Social-Ecological Systems Framework (SESF) as a diagnostic tool with 52 indicators to assess the sustainability of groundwater resources.

New hydrological insights for the region

Based on key informant interviews with local experts and stakeholders, we use the TOPSIS technique and the Shannon Entropy methodologies to weigh and rank indicators influencing sustainability. Findings revealed that the indicators within the category Resource Systems (RS) and Resource Units (RU) with values of 0.74, and 0.70, are the most stable contributing factors to local sustainability, respectively. In contrast, the Governance System (GS), Actor (A), and Interaction (I) first-tier variables were evaluated as less stable, along with Outcomes (O). This suggests that social factors and diverse outcomes may need further attention in the region to ensure management and policy development that can better enable sustainable outcomes. This analysis also demonstrates the usefulness of a comprehensive science-based framework for organizing, analyzing, and presenting a wide range of complex information to inform policymakers and planners.