Changes In Hydrological Regime Research Articles

River Hydrological Regime Changes and Their Attribution: A Case Study in the Upper Reaches of the Yangtze River Using a Multi‐Model Approach

River Hydrological Regime Changes and Their Attribution: A Case Study in the Upper Reaches of the Yangtze River Using a Multi‐Model Approach

Hydrographic shifts in coastal waters reflect climate-driven changes in hydrological regimes across Northwestern Patagonia

Climate-driven changes in freshwater inputs have been shown to affect the structure and function of coastal ecosystems. We evaluated changes in the influence of river runoff on coastal systems of Northwestern Patagonia (NWP) over recent decades (1993–2021) by combined analysis of long-term streamflow time series, hydrological simulation, satellite-derived and reanalysis data on sea surface conditions (temperature, turbidity, and salinity). Significant decreases in minimum streamflow across a zone spanning six major river basins were evident at weekly, monthly, and seasonal scales. These changes have been most pronounced in mixed-regime northern basins (e.g., Puelo River) but appear to be progressing southward to rivers characterised by a nival regime. In the adjacent two-layer inner sea, reduced freshwater input corresponds with a shallower halocline and increased surface temperatures across northern Patagonia. Our results underscore the rapidly evolving influence of rivers on adjacent estuarine and coastal waters in NWP. We highlight the need for cross-ecosystem observation, forecasting, mitigation and adaptation strategies in a changing climate, together with corresponding adaptive basin management of systems that supply runoff to the coastal marine waters.

Development of a comprehensive framework for quantifying the collective and individual influence of climate change and human activities on hydrological regimes

Previous research rarely identified the synergistic effects of climate change and human activities on hydrological regimes, thus leading to an incomplete attribution of hydrological regime changes. To address this issue, this paper presents a complete approach for accurately quantifying these impacts. The framework integrates various methodologies, including the runoff abrupt change point judgment method for distinguishing pre- and post-impact periods, The Soil and Water Assessment Tool (SWAT) is used to isolate runoff processes influenced solely by climate change, the linear separation method for identifying runoff processes affected solely by human activities, and the Indicator of Hydrologic Alteration (IHA) for quantifying changes in hydrological regimes. Application of this framework to the Ganjiang River Basin (GRB) unveils significant alterations in hydrological regimes. This has resulted in a significant decline in aquatic organism species compared to the prior-impact period levels. Notably, climate change and human activities exert opposing effects on minimum flow indicators and flow pulse indicators in the GRB. Moreover, these factors exhibit a substantial synergistic effect on numerous indicators, resulting in hydrological regimes combined influenced by climate change and human activities being considerably different with the cumulative impact on hydrological regimes solely influenced by climate change and those solely influenced by human activities. Consequently, in future water management, it is crucial to recognize the positive role of prudent human activities in mitigating the adverse impacts of climate change.

Climate change and the taphonomic signature of Neolithic mounds: the Kur River Basin over five decades of satellite imagery coverage

ABSTRACT This paper discusses the impact of modern land use and climate change on mounded prehistoric sites, considering the evidence from Kur River Basin (southwestern Iran). By applying remote sensing and GIS techniques to historical and recent satellite imagery, we monitored an assemblage of 45 Neolithic mounds in order to map and quantify their taphonomic signatures over the last 53 years. Our results highlight that the deterioration of sites occurred as a result of landscape transformation due to land use and socio-economic dynamics that were exacerbated by current climate change. Increasing demands for fertile land and water led to the over-exploitation of sources, resulting in changing hydrological regimes and ecological systems and loss of the archaeological record. By contextualizing these processes over a historical perspective, our findings contribute to archaeological heritage management efforts.

Hydro-climatic extremes shift the hydrologic sensitivity regime in a cold basin

Escalating climate extreme events disrupt hydrological processes by affecting both water availability and sediment dynamics. However, the interconnection between hydrological variability and climatic extremes remains underexplored, particularly in cold regions under a changing climate. Here, we develop a yield-based dichotomy framework to examine the impact of shifted climatic extreme patterns on hydrological regimes in the Ishikari River Basin (IRB), Hokkaido, Japan, which is a crucial area for local agriculture and urban development. Utilizing a modified Soil and Water Assessment Tool (SWAT) integrated with downscaled CMIP6-GCM climate projections under Shared Socioeconomic Pathways (SSPs) scenarios, we identified significant annual variability in water and sediment yields associated with extreme climate events. Hot-dry conditions correlate with lower water and sediment yields, whereas increased cold extremes may result in higher sediment yields across the IRB. Our findings also indicate that hotter and drier patterns interact with hydrological processes, potentially establishing new hydrologic regimes and shifting climatic extremes-induced thresholds for yield classification within the IRB. Notably, under SSP585, both water availability and sediment transport are projected to intensify, increasing flood risks and exacerbating sedimentation challenges. Our study highlights the urgent need for adaptive water management strategies to address these anticipated changes in hydrological regimes in response to global climate change.

Assessing the effectiveness of reservoir operation and identifying reallocation opportunities under climate change

Reservoirs are designed and operated to mitigate hydroclimatic variability and extremes to fulfill various beneficial purposes. Existing reservoir infrastructure capacity and operation policies derived from historical records are challenged by hydrologic regime change and storage reduction from sedimentation. Furthermore, climate change could amplify the water footprint of reservoir operation (i.e. non-beneficial evaporative loss), further influencing the complex interactions among hydrologic variability, reservoir characteristics, and operation decisions. Disentangling and quantifying these impacts is essential to assess the effectiveness of reservoir operation under future climate and identify the opportunities for adaptive reservoir management (e.g. storage reallocation). Using reservoirs in Texas as a testing case, this study develops data-driven models to represent the current reservoir operation policies and assesses the challenges and opportunities in flood control and water supply under dynamically downscaled climate projections from the Coupled Model Intercomparison Project Phase 6. We find that current policies are robust in reducing future flood risks by eliminating small floods, reducing peak magnitude, and extending the duration for large floods. Current operation strategies can effectively reduce the risk of storage shortage for many reservoirs investigated, but reservoir evaporation and sedimentation pose urgent needs for revisions in the current guidelines to enhance system resilience. We also identify the opportunities for reservoir storage reallocation through seasonal-varying conservation pool levels to improve water supply reliability with negligible flood risk increase. This study provides a framework for stakeholders to evaluate the effectiveness of the current reservoir operation policy under future climate through the interactions among hydroclimatology, reservoir infrastructure, and operation policy.

Biodiversity of testate amoebae in Sphagnum bogs: the dataset from forest-steppe ecotone (Middle Volga Territory, Russia).

Testate amoebae are a polyphyletic group of unicellular eukaryotic organisms that are characterised by a rigid shell and inhabit mostly freshwater and terrestrial ecosystems. They are particularly abundant in peatlands, especially in Sphagnum-dominated biotopes. Peatland hydrology is the most important influence on testate amoebae communities. The good preservation of the shells in peat deposits and their response to hydrological regime changes are the principles for palaeohydrological reconstructions. Any changes in the water balance of mires should be expected to have far-reaching effects on biogeochemical cycles, productivity, carbon dioxide and methane exchange. This paper presents a dataset (Darwin Core Archive - DwC-A) on the distribution of Sphagnum-dwelling testate amoebae in nine mires located in the forest-steppe subzone of the East European Plane. The dataset includes information about 86 taxa belonging to 29 genera and contains 3,123 occurrences of 49,874 individuals. The following environmental variables are provided: microtopography, oxidising and reducing potential, total mineralisation, substrate temperature, acidity, substrate wetness and water table depth. These data might be used for biogeographical and palaeoecological studies, including quantitative reconstructions.

Assessing the effects of dam regulation on multiscale variations in river hydrological regime and ecological responses

ABSTRACT Using a combination of the long short-term memory model and hydrological change indicators, this study proposes an assessment framework at inter-annual and intra-annual scales to quantify the hydrological regime changes and ecological event responses caused by the regulation of the Three Gorges Dam (TGD) in the upper reaches of the Yangtze River. The results indicate that during the post-TGD period (2004–2019), 2 indicators of the natural flow regime undergo a high degree of alteration at the inter-annual scale, which increase to 12 when regulated flows are considered. Furthermore, we find that while climate and incoming water change significantly reduces the annual flow and monthly flow during the flood season, it increases the complexity (79%) and ecodeficit at the seasonal scale (94%). Among the 32 indicators of hydrologic alteration, TGD is the dominant factor influencing changes in 20 indicators, increasing the magnitude of low-flow events, decreasing the frequency of high-flow pulses, and advancing the timing of 1-day minimum flow (43 Julian date). From the hydrological perspective, the altered rising water conditions due to TGD regulation may cause an average decrease of 19.5% in the fry abundance for the Four Famous Major Carps.

How does the daily regulation hydropower station reduce the hydrological regime impact? A case study in upper Yellow River

ABSTRACT Human activities, particularly the regulation of hydropower stations, have profoundly altered river flow patterns. While studies have extensively assessed the impact of large or multi-year regulated hydropower stations on hydrological regimes using indicators of hydrological alteration (IHA) and range of variability approach (RVA), the impact of daily regulation hydropower stations has received comparatively less attention. This study aims to evaluate the influence of daily regulation hydropower stations on hydrological regime changes, focusing on the upper Yellow River region in China. Using daily runoff data from 1954 to 2020 at the Guide station, the study compares the impacts of multi-year regulated (Longyangxia) and daily regulation (Laxiwa and Nina) hydropower stations. The Mann-Kendall test showed that 27 out of 32 Indicators of Hydrological Alteration (IHAs) had significant trends under Longyangxia operation, which reduced to 18 IHAs with the inclusion of daily regulation stations. The Range of Variability Approach (RVA) revealed that only 46.87% of IHAs exhibited high alteration from the natural regime when daily regulation was considered, down from 75.00% with Longyangxia alone. This suggests that daily regulation can mitigate the negative impacts of multi-year regulation, potentially enhancing the river's eco-hydrological health.

Unveiling hydrological dynamics in data-scarce regions: experiences from the Ethiopian Rift Valley Lakes Basin

Abstract. The hydrological system of the Rift Valley Lakes in Ethiopia has recently experienced changes over the past 2 decades. Potential causes for these changes include anthropogenic, hydro-climatic, and geological factors. The main objective of this study was to utilize an integrated methodology to gain a comprehensive understanding of the hydrological systems and potential driving factors within a complex and data-scarce region. To this end, we integrated a hydrologic model, change point analysis, indicators of hydrological alteration (IHA), and a bathymetry survey to investigate hydrological dynamics and potential causes. A hydrologic model (the Soil and Water Assessment Tool Plus, SWAT+) was parameterized for the gauged watersheds and extended to the ungauged watersheds using multi-site regionalization techniques. The SWAT+ model performed very well to satisfactorily for daily streamflow in all watersheds with respect to the objective functions of the Kling–Gupta efficiency (KGE), the Nash–Sutcliffe efficiency (NSE), and percent bias (PBIAS). The findings reveal notable changes in lake inflows and lake levels over the past 2 decades. Lake Chamo experienced an increase in area of 30.1 km2 (9.5 %), an increase in depth of 4.4 m (30.9 %), and an increase in volume of 7.8×108 m3 (27.2 %). In contrast, Lake Abijata witnessed an extraordinary 68 % decrease in area and a depth decrease of 1.6 m (37.2 %). During the impact period, the mean annual rainfall experienced a decrease of 6.5 % and 2.7 % over Lake Abijata and Lake Chamo, respectively. Actual evapotranspiration decreased by 2.9 % in Lake Abijata but increased by up to 4.5 % in Lake Chamo. Surface inflow to Lake Abijata decreased by 12.5 %, while Lake Chamo experienced an 80.5 % increase in surface inflow. Sediment depth in Lake Chamo also increased by 0.6 m (4.2 %). The results highlight that the changing hydrological regime in Lake Chamo is driven by increased surface runoff and sediment intrusion associated with anthropogenic influences. The hydrological regime of Lake Abijata is affected by water abstraction from feeding rivers and lakes for industrial and irrigation purposes. This integrated methodology provides a holistic understanding of complex data-scarce hydrological systems and potential driving factors in the Rift Valley Lakes in Ethiopia, which could have global applicability.

Modeling the impacts of oil palm plantations on water quantity and quality in the Kais River Watershed of Indonesia

Oil palm plantations can impact hydrological processes in many tropical watersheds. The rapid conversion of tropical rainforests for commercial operations in recent decades has been associated with water scarcity, flooding, and polluted rivers. However, this widespread and emerging issue is less studied and underreported due to limited data availability, modeling complexity, and the remote nature of these landscapes. Ecohydrologic modeling enables us to investigate changes in watershed conditions caused by large-scale land cover changes from plantations. This study examines the impact of oil plantations on water quantity and quality using the SWAT+ model in the Kais River Watershed, West Papua, Indonesia. The objective is to assess the hydrological changes concerning land cover conversion to oil palm plantations. Results show that establishing oil palm plantations increased surface runoff by 21 %, and sediment yields rose by 16.9 % compared to the baseline. There was also a significant increase of 78 % in mean annual total nitrogen and 144 % in total phosphorous after the plantations' establishment. The results show that forest conversion to oil palm plantations in the Kais River watershed is a primary driver of change in hydrological regimes, resulting in the deterioration of water quality. There is a need for conservation strategies to mitigate the impacts of significant landscape changes in watershed ecosystems.

Influence of seasonal hydrological regimes on benthic macroinvertebrates in two the Brazilian biodiversity hotspots

Global warming has changed climate patterns worldwide causing an increase of extreme weather conditions that have altered annual seasonal hydrological regimes. These extreme climate-driven shifts modify habitat availability and can influence freshwater communities in disruptive ways. Our study investigates how changes in annual seasonal hydrological regimes affect the community structure and the Functional Feeding Groups (FFG) of benthic macroinvertebrates in two Brazilian biodiversity hotspots, the Brazilian Tropical Savannas (a.k.a., Cerrado) and Atlantic Forest biomes. We investigate whether annual variation in precipitation between biomes influence composition, richness, and abundance of benthic macroinvertebrates and their proportions of FFG. We demonstrate that differences in annual precipitation rates affect the composition and abundance, but not richness of benthic macroinvertebrates. Changes in community structure are related to changes in annual precipitation, which modify stream variables. Our findings suggest that annual seasonal changes in hydrological precipitation modify benthic macroinvertebrate communities, especially in Cerrado, where dry seasons are more pronounced. Therefore, annual changes in precipitation rates may disrupt the benthic macroinvertebrate communities in tropical savannas, potentially leading to biodiversity loss.

Clumped Isotopes Record a Glacial‐Interglacial Shift in Seasonality of Soil Carbonate Accumulation in the San Luis Valley, Southern Rocky Mountains, USA

AbstractClumped isotope paleothermometry using pedogenic carbonates is a powerful tool for investigating past climate changes. However, location‐specific seasonal patterns of precipitation and soil moisture cause systematic biases in the temperatures they record, hampering comparison of data across large areas or differing climate states. To account for biases, more systematic studies of carbonate forming processes are needed. We measured modern soil temperatures within the San Luis Valley of the Rocky Mountains and compared them to paleotemperatures determined using clumped isotopes. For Holocene‐age samples, clumped isotope results indicate carbonate accumulated at a range of temperatures with site averages similar to the annual mean. Paleotemperatures for late Pleistocene‐age samples (ranging 19–72 ka in age) yielded site averages only 2°C lower, despite evidence that annual temperatures during glacial periods were 5–9°C colder than modern. We use a 1D numerical model of soil physics to support the idea that differences in hydrologic conditions in interglacial versus glacial periods promote differences in the seasonal distribution of soil carbonate accumulation. Model simulations of modern (Holocene) conditions suggest that soil drying under low soil pCO2 favors year‐round carbonate accumulation in this region but peaking during post‐monsoon soil drying. During a “glacial” simulation with lowered temperatures and added snowpack, more carbonate accumulation shifted to the summer season. These experiments show that changing hydrologic regimes could change the seasonality of carbonate accumulation, which in this study blunts the use of clumped isotopes to quantify glacial‐interglacial temperature changes. This highlights the importance of understanding seasonal biases of climate proxies for accurate paleoenvironmental reconstruction.

Editorial Wetlands for human well-being

Editorial Wetlands for human well-being

Flood mapping of the lower Mejerda Valley (Tunisia) using Sentinel-1 SAR: geological and geomorphological controls on flood hazard

Understanding the influence of the hydrological regime changes, encompassing both the duration and spatial extent of floods, is explored, through this paper, in the context of the complex interactions of the geological, geomorphological and climate change conditions. Integrating these parameters and their combined influence becomes paramount for effective flood risk management and disaster prevention, as highlighted in the broader context of the study’s conclusions. Over the past decade, despite prevailing drought conditions in North African countries, the Mejerda Valley in Tunisia has experienced several major flood events. The valley geomorphological history is presented, within the landscape evolution. This study explores the use of Sentinel-1 radar data for detecting and managing floods in the region, with a particular emphasis on the vulnerability of the Lower Mejerda Valley. Sentinel-1 radar data, owing to their continuous monitoring capabilities independent of weather conditions, prove highly effective in tracking the temporal evolution of floods and accurately mapping the extent of affected areas. The methodology utilized in this study has proven to be highly effective in accurately identifying areas susceptible to flooding, both spatially and temporally. In generating classified flood images, water objects are highlighted by applying a specific formula. The study delves into significant flood events in the Mejerda Valley, including occurrences in 2015, 2017, 2019, and 2020, examining their profound impacts on various regions. For instance, the floods of 2015 recorded precipitation levels reaching up to 141 mm, contributing to the overall understanding of flood evolution in the region. In conclusion, the Mejerda Delta’s relief is primarily due to tectonism, influencing both Mio-Pliocene and Quaternary processes, shaping the current delta configuration. The Valley’s topography results from extensive geomorphological evolution, with the eastward shoreline advance leading to the formation of sebkhas and lagoons, indicators of high flood risk, supported by detailed flood event analysis. Moreover, The climate change and anthropic activity are non-negligible parameters influencing flood occurrence and intensity.

Pairing remote sensing and clustering in landscape hydrology for large-scale change identification: an application to the subarctic watershed of the George River (Nunavik, Canada)

Abstract. For remote and vast northern watersheds, hydrological data are often sparse and incomplete. Landscape hydrology provides useful approaches for the indirect assessment of the hydrological characteristics of watersheds through analysis of landscape properties. In this study, we used unsupervised geographic object-based image analysis (GeOBIA) paired with the fuzzy c-means (FCM) clustering algorithm to produce seven high-resolution territorial classifications of key remotely sensed hydro-geomorphic metrics for the 1985–2019 time period, each with a frequency of 5 years. Our study site is the George River watershed (GRW), a 42 000 km2 watershed located in Nunavik, northern Quebec (Canada). The subwatersheds within the GRW, used as the objects of the GeOBIA, were classified as a function of their hydrological similarities. Classification results for the period 2015–2019 showed that the GRW is composed of two main types of subwatersheds distributed along a latitudinal gradient, which indicates broad-scale differences in hydrological regimes and water balances across the GRW. Six classifications were computed for the period 1985–2014 to investigate past changes in hydrological regime. The time series of seven classifications showed a homogenization of subwatershed types associated with increases in vegetation productivity and in water contents in soil and vegetation, mostly concentrated in the northern half of the GRW, which were the major changes occurring in the land cover metrics of the GRW. An increase in vegetation productivity likely contributed to an augmentation in evaporation and may be a primary driver of fundamental shifts in the GRW water balance, potentially explaining a measured decline of about 1 % (∼ 0.16 km3 yr−1) in the George River’s discharge since the mid-1970s. Permafrost degradation over the study period also likely affected the hydrological regime and water balance of the GRW. However, the shifts in permafrost extent and active layer thickness remain difficult to detect using remote-sensing-based approaches, particularly in areas of discontinuous and sporadic permafrost.

The development of inflow discharge for the karian multipurpose reservoir in the pursuit of reservoir management optimization

Climate change and land cover modifications result in alterations in hydrological regimes. The demand for water and electrical energy continually rises along with population growth. Consequently, optimizing the Karian Multipurpose Reservoir (Hydroelectric Exploitation) operation requires considering hydrological regime changes. The Karian multipurpose reservoir is designed to meet water needs in Banten Province. The strategic policy for the Reservoir is to provide raw water at a rate of 14.6 m3/s. Of this, 9.1 m3/s is diverted to Tangerang Regency, and 5.5 m3/s is directed to Serang City through Ciujung River. Before being released into the Ciujung River, a flow of 5.5 m3/s is channeled through turbines to generate 1.8 MW of electricity. This study compares two models for estimating discharge to support Karian Reservoir management: (1) The Rainfall Conversion Ratio (CR) and Catchment Area, and (2) The Continuous model. The Rainfall CR and Catchment Area has a correlation value of 0.523 with CR KOICA, Absolute Relative Error (ARE) of 0.54, and Root Mean Square Error (RMSE) of 10.61. Meanwhile, the continuous model has a correlation value of 0.877 with CR KOICA, ARE of 0.18, and RMSE of 3.64. The results indicate the continuous model is the most effective in estimating input discharge.

Development of multivariate standardized drought index for large lake basins based on the copula function: A case study of Hongze Lake Basin, China

Study regionThe Hongze Lake Basin, China. Study focusA drought index is an essential tool for monitoring and prediction, and the construction of a comprehensive drought index is at the cutting edge of current drought research. Considering the regulation effect of lakes, a new drought index aimed at large lake catchment areas, namely the Multivariate Standardized Drought Index for Lakes Basin (MSDILB), can comprehensively characterise meteorological and hydrological drought. Here, the Standardised Precipitation Evapotranspiration Index (SPEI), Standardised Runoff Index (SRI), and MSDILB drought indices were used to evaluate the evolution of drought in the study area. Moreover, the response and conversion relationships between the basin’s hydro-meteorological elements and the regulation of the lake were explored. New hydrological insights for the RegionThe results indicate that: 1) in a dry year, the spatial-temporal heterogeneous runoff in the basin is redistributed by the storage and regulation of large lakes, thereby reducing the frequency of drought events; 2) the MSDILB drought index merges the characteristics of hydrological drought and meteorological drought indices and can monitor the evolution of drought events in lake basins; 3) the MSDILB drought index can sensitively capture the effects of lake hydrological regime change on drought events in the basin. Thus, it has the advantage of comprehensively characterising the drought conditions in large lake basins.

Response of lake metabolism to catchment inputs inferred using high‐frequency lake and stream data from across the northern hemisphere

AbstractIn lakes, the rates of gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NEP) are often controlled by resource availability. Herein, we explore how catchment vs. within lake predictors of metabolism compare using data from 16 lakes spanning 39°N to 64°N, a range of inflowing streams, and trophic status. For each lake, we combined stream loads of dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP) with lake DOC, TN, and TP concentrations and high frequency in situ monitoring of dissolved oxygen. We found that stream load stoichiometry indicated lake stoichiometry for C : N and C : P (r2 = 0.74 and r2 = 0.84, respectively), but not for N : P (r2 = 0.04). As we found a strong positive correlation between TN and TP, we only used TP in our statistical models. For the catchment model, GPP and R were best predicted by DOC load, TP load, and load N : P (R2 = 0.85 and R2 = 0.82, respectively). For the lake model, GPP and R were best predicted by TP concentrations (R2 = 0.86 and R2 = 0.67, respectively). The inclusion of N : P in the catchment model, but not the lake model, suggests that both N and P regulate metabolism and that organisms may be responding more strongly to catchment inputs than lake resources. Our models predicted NEP poorly, though it is unclear why. Overall, our work stresses the importance of characterizing lake catchment loads to predict metabolic rates, a result that may be particularly important in catchments experiencing changing hydrologic regimes related to global environmental change.

The Present-Day Structure of the Temperature and Current Fields in Lake Sevan

Long-term features of the vertical and horizontal structure of water temperature field in Lake Sevan are discussed. It is shown that the climate warming has led to an increase in epilimnion temperature in Bol’shoi Sevan in July by 2.0‒3.0°C. The increase in water temperature in hypolimnion was not greater than 1.1°C. In autumn (October), the epilimnion became 1.2°C warmer, while hypolimnion temperature practically has not changed on the average over years. Temperature fields were used to calculate the density currents in summer and autumn periods. A dominating cyclonic water circulation was revealed all over the lake, confirmed by chlorophyll distribution by satellite image data. In the case of large horizontal gradients of water density, the flow velocity can reach 50 cm/s. Autonomous buoy stations revealed a wide range of water temperature variations due to internal waves of different nature. The reversible vertical mixing of water mass by internal waves plays an important role in the distribution of nutrients and plankton within the water mass. The water level rise by ~3 m, unlike it drop by 1981 by 18.48, has not caused any significant changes in lake hydrological regime.