Journal of Hydrology-Regional Studies最新文献

Study region

The study region is a typical desert oasis ecotone of the Hexi Corridor, Northwest China.

Study focus

Based on four years of in situ observational data of soil water, temperature, and electrical conductivity obtained from three Haloxylon ammodendron (H. ammodendron) forests (20, 30 and 50 years) in a typical desert oasis ecotone (DOE) of the Hexi Corridor, in this study, the mechanisms of change and coupled effects of water, heat, and salt in frozen desert soils along a long-term shrub plantation in a typical desert oasis ecotone are presented.

New hydrological insights for the region

This study revealed that changes in soil water, heat, and salt and their coupling effects were completely different between shallow (0–80 cm) and deep (160–200 cm) depths. At 0–80 cm, soil water gradually decreased in the 50-year-old H. ammodendron plot, but soil salt first increased in the 30-year plot and then decreased in the 50-year plot. When the freezing process occurred in the 0–80 cm depth interval, the soil water and salt contents decreased nonlinearly with the absolute value of the soil temperature (|T|), following a power function and logarithmic function, respectively. For the thawing process in the 0–80 cm depth interval, soil water and salt increased with increasing temperature, and there was a significant linear relationship between soil water and salt (P<0.01). In the 160–200 cm layer, soil water and salt significantly increased after 30–50 years during the growing season.

Study region

The three headwaters of Tarim river, south of the Xinjiang Province, China.

Study focus

Temporal runoff concentration variations are crucial for water resources utilization and management, particularly in arid regions. In this study, the runoff concentration in the Tarim River Basin is studied based on analysis of the trend, abrupt changes, and periodicity, identifying key extreme climate indices influencing the Gini-runoff coefficient and predicting its future changes under three Shared Socioeconomic Pathways (SSPs).

New hydrological insights for the region

From 1962–2020, the Gini-runoff coefficient decreased by 8.3 %, while annual runoff increased by 14.2 %. This is attributed to temperature changes, escalating hydrological risk uncertainty. The anomaly of low geopotential high fields and Central Asian anticyclones have caused an increase in total cloud cover (TCC) and precipitation, and a decrease in the Daily Temperature Range (DTR). Increasing of Warm nights (TN90), Maximum Tmax (TXx), and Hot nights (TR) have enhanced the warm-season runoff. However, the climatic impact on warm-season runoff is less pronounced than that in the cold season, which led to the runoff concentration decline. Changes in hydro-junction regulation led to decrease of Gini-runoff coefficient by 12.11 % from 2001 to 2020 along the Hotan river. Under the three SSP scenarios, the average Gini-runoff coefficient for the Aksu and Hotan rivers are expected to decrease by 3.3 % and 2.6 %, respectively.

Study region

The Seohwa watershed, South Korea.

Study focus

Agricultural practices and urbanization in watersheds increase nutrient loads (total nitrogen (TN), total phosphorus (TP), and nitrate-nitrogen (NO₃^--N)) in streams and deteriorate water quality. Between October 2017 and October 2018, water samples were collected from a small stream (MS), main tributary (TS), and sub-tributaries (ST) characterized by different land-use patterns. The objective of this study was to identify the sources that determine water quality in the respective streams and to estimate whether water quality was dependent on land-use patterns.

New hydrological insights for the region

TN in MS progressively decreased downstream, whereas such spatial variation was not observed in TS and ST. For TP, TS and ST samples showed elevated concentrations during storm events, but not in MS. These observations resulted from TN and TP derived from natural and anthropogenic sources associated with land-use patterns. Interestingly, TN/TP ratios were strongly negatively correlated with the proportion of residential area (R² = 0.92) rather than other land-use patterns such as agricultural area and forest. In addition, statistical analysis and dual isotopes of nitrate (NO₃^-) showed that the water quality in MS and the one in TS and ST were predominantly affected by natural sources and anthropogenic sources, respectively. Considering the effects of land-use patterns and rainfall on water quality, anthropogenic sources should be precisely identified to manage stream water in small watersheds more effectively.

Study region

A valley area in South Korea

Study focus

Sand dams are cost-effective water-storage facilities for water-stressed areas in arid and semi-arid climates, with the advantages of reducing evaporation losses and filtering pollutants. Generally, sand dams are constructed by placing a horizontal barrier across the river bed, creating a naturally sand-filled structure upstream. Unlike this typical construction, a sand dam in Korea in the monsoon climate region was built near a mountainous valley, not in a stream, in Mulori, Chuncheon City, to ensure a sustainable water supply throughout the year, and especially to prevent freezing in the winter. Furthermore, a small-scale groundwater dam was additionally constructed downstream of the sand dam to increase the water supply capacity in preparation for severe droughts. In this study, the hydrological reservoir-routing simulations were performed to evaluate the effects of the combined use of the two dams on increasing water supply.

New hydrological insights for the region

Daily discharge rates for the period from March 16, 2020 to July 6, 2022 were simulated for several hybrid operations that supplies water primarily through the sand dam under the normal conditions, but combines both water sources to manage severe droughts. The simulated results showed that, compared with operating the sand dam alone, the hybrid operations could satisfy the village’s water demand by increasing the minimum water supply rates by 24.6–50.0 m³/day for different simulation conditions. The combined use of sand and groundwater dams presented in this study will help provide sustainable water supply in water-stressed areas, especially mountainous uplands vulnerable to droughts and freezes.

Study Region

China.

Study Focus

Water resources are one of the indispensable and irreplaceable natural resources in the operation of social and economic sustainable development. When economic measures are used to manage water resources, the market mechanism can be used to fully optimize resource allocation and boost water use efficiency (WUE). While existing research have begun to explore the impact of water rights trading (WRT) on WUE, most remain theoretical, with empirical studies often neglecting time differences in WRT implementation across provinces, leading to unresolved endogeneity issues. To accurately assess the policy effects of WRT, our research constructs a multi-period DID mode that addresses these limitations.

New Hydrological Insights for the Regions

This study reveals that WRT significantly improves WUE, with water use per unit of output decreasing by 574.724 units in agriculture, 366.136 units in industry, and 210.770 units overall, demonstrating robustness. The policy effects of WRT require time to materialize, showing both dynamic and spatial sustainability. Technological innovation (TEIN) and water factor mobility (FM) serve as intermediary variables through which WRT optimizes WUE, with TEIN exhibiting a masking effect on WUE improvement. These insights can contribute to improved water resource management globally by guiding the development of tailored water rights policies and strategies that incorporate market mechanisms, foster technological innovation, and improve overall WUE.

Study area

Yangtze River Basin, China.

Study focus

The surface water area (SWA) of the Yangtze River Basin (YRB) has changed significantly due to intensified human interferences. But no study investigated the variations in different water types and its drivers yet. To figure out the long-term changes in water bodies and the underlying driving forces, an improved method based on satellite data was developed to accurately delineate the seasonal SWA of the YRB from 1990 to 2020. Changes in different categories (reservoirs, lakes, and rivers) of water bodies are discriminated and attributed to various climatic and anthropogenic factors.

New hydrological insights for the region

Trend of the total SWA in the YRB was non-significant, but obvious changes happened at sub-basin scale. The SWA in the source region and upper reaches demonstrated an upward trend, while a decline was observed in the middle and lower reaches. The increase is largely attributed to reservoir changes (70 %). While, the decreases are attributed to changes in lakes (45 %) and rivers (55 %). Attribution analysis reveals that climatic factors primarily drive the SWA changes in the source region (74 %), while human activities play a more substantial role in the upper reaches (64 %). For the middle and lower reaches, climate and human activities have equally influences. This study shed light on the significant impact of human activities on the redistribution of SWA.

Study region

In this study, we compared the spatiotemporal evolution of rainfall trends in E-OBS and ERA5 to those detected using historical rainfall series recorded by ground-based networks in Southern Italy. In particular, the study is applied to the Campania, Basilicata, Apulia, Calabria and Sicily regions (84,000 km² in total) on seasonal and annual scales.

Study focus

Meteorological gridded datasets at large spatial scales are widely used in many hydroclimatic applications as they provide long and spatially homogeneous records. Regional trend analyses based on these data need to be treated with caution due to some potential limitations at relevant hydrological scales, such as the coarse spatial resolution and the spatio-temporal inhomogeneity of the underlying data. Gradual trends and abrupt change points were studied on rainfall data from 1979 to 2019.

New hydrological insights for the region

Both gridded datasets capture the major trends in observed rainfall, with a predominance of positive values driven by changes in September-November. Overall, ERA5 returns flatter results compared to E-OBS, with the former comparing well with observations in Sicily and Apulia, while the latter is performing well in Campania and partially in Calabria and Basilicata. Most statistically significant trends are associated with discontinuities in the early 2000s, and this is well captured by both ground and gridded datasets. The general behavior in inter-annual variability trends in Southern Italy is captured by both datasets, with ERA5 also detecting regional patterns.

Study region

River basins in the Tibetan Plateau, including the Yarlung Zangbo River (YZR) basin, the Salween River (SWR) basin, the Lancang River (LCR) basin, the Yangtze River (YTR) basin, the Yellow River (YLR) basin, and the Tarim River (TRM) basin.

Study focus

In recent years, the concept of seasonal catchment memory has emerged as a pivotal element in the field of hydrological science. Precipitation memory curve (PMC) is a good method to describe seasonal precipitation memory process, which is the key function connecting precipitation and terrestrial water storage change (TWSC). The model simulated TWSC with precipitation is proposed based on PMC. According to the performance of the model, this study investigates optimal curve functions to describe seasonal catchment memory in the Tibetan Plateau.

New hydrological insights for the region

It is found that in most basins, the shape of PMC is consistent with the Boussinesq function or Maillet function. In the SWR basin, PMC varies between warm season and cold season. However, due to relatively less precipitation in the cold season compared to the warm season, the segmented-representation PMC has only a slight improvement on the TWSC simulation. In the TRM basin, the temperature-index method can improve the performance of the model. The PMC of the TRM basin during the warm season exhibits a short duration of precipitation memory of approximately three months.

Study region

Lake Bogoria and Lake Baringo, Rift Valley, Kenya

Study focus

Starting around 2010, several of Kenya’s Rift Valley lakes experienced significant rises in water levels. There is presently fear of an ecological catastrophe should the water levels of the alkaline Lake Bogoria continue to rise and subsequently overflow into and cross-mix with the freshwater Lake Baringo, a hydrological situation witnessed ∼8 000–10 000 years ago.

New hydrological insights into the region

In the last decade, data reveals significant meteorological and hydrological changes in the study region. Average annual rainfall has more than doubled, with substantial increases in variability. Despite a decrease in the number of rainy days within this period, intense rainfall days have increased by 318 %. Relative to the maximum water level observed in 2020, a 0.7 m increase in lake level would be sufficient for Lake Bogoria to reach the spill point located at about 1000.2 m, beyond which an overflow into Lake Baringo begins to occur. In 2023, the lake level declined by 1.5 m, resulting in a decreased risk of overflow of ∼20 %. Results indicate that mean annual rainfall after 2010 was high enough to provide an average annual flow of 500–1000 L/s from Lake Bogoria towards Baringo if lake levels were at spill point elevation.

Study region: The Ailaoshan National Nature Reserve forest is a mountainous water catchment area for the Lancang River basin and a subtropical ecological conservation area in southwest China. Study focus: The study aimed to understand how water fluxes in a subtropical forest responds to extreme weather disturbances and their recoveries in the post-damage years. We used eddy covariance data (2010–2019) to investigate the evapotranspiration (ET), transpiration (T), evaporation (E), and canopy conductance (Gc) before and after an extreme snow event in 2015. New Hydrological Insights: In the snow damage year, the leaf area index (LAI) decreased by 49 % compared to the pre-damage levels. The severe vegetation damage caused a significant decrease in ET, T, E, and Gc by 35 %, 36 %, 23 %, and 33 %, respectively, compared to the pre-damage levels. T returned to its pre-damage level in 2016, one year after the snow damage. In contrast, LAI, ET, E and Gc recovered to their pre-damage levels in 2018, four years after the initial damage. Reduced ET caused a strong positive RF_ET, which diminished forest evaporative cooling and resilience. Our results suggest that the delayed E recovery enables water reserves in the ecosystems to be used through T to support rapid understory vegetation growth. This mechanism plays critical in bolstering ecosystem resilience as it facilitates swift recovery following disturbances in subtropical forests.