Streamflow Analysis Research Articles

Changes in snowmelt runoff timing in the contiguous United States

AbstractChanges in timing of snowmelt‐fed streamflow have great importance for water supply, flood management, and ecological processes, as well as being a common indicator of climate change. In this study, snowmelt runoff timing change in the contiguous United States between 1957 and 2016 was investigated by analysing data from 97 streamflow gages. The annual snowmelt runoff timing shift was identified using ‘Center Time (CT)’ and ‘Spring Pulse Onset (SPO)’ methods, jointly with the monthly fractional streamflow (MFS) analysis, conducted between January and June. Since snowmelt‐derived streamflow timing change is mainly induced by regional meteorological factors, such as air temperature and precipitation, their trends and relationship with CT were also examined. Shifts toward earlier snowmelt runoff timing were found by both methods, CT (8.3 days on average) and SPO (8.5 days on average). Although the results of the CT change are stronger than the SPO change, both outcomes are mostly correlated, particularly in the central and northwestern parts of the country. MFS trends support the outcomes of CT and SPO. In January, February, and especially March, a higher number of the stations indicated increasing trends in MFS. In April, May, and June, their number decreased and the number of gages with diminishing trends rose sharply. The timing difference is highly related to temperature change. Annual average temperature and temperature in the melting period increase considerably. The annual average temperature is significantly negatively correlated with CT in the vast majority of the regions. Although precipitation is not as effective as the temperature, its trends have impacts on snowmelt runoff timing change depending on the region and elevation. These results demonstrate the importance of the impacts of snowmelt runoff timing changes due to global warming on the regional and large‐scale hydrology in the contiguous United States.

Spatiotemporal hydrological analysis of streamflows and groundwater recharge for sustainable water management in Prince Edward Island, Canada

AbstractPrince Edward Island (PEI), Canada, entirely depends on groundwater for freshwater supplies, which also highly feeds streamflows. In a few watersheds, pumping has had disturbed steady‐state conditions and reduced streamflows. Spatiotemporal hydrological analysis of streamflows and recharges was performed in its scattered watersheds. Mill, Wilmot, West, Winter, and Bear River watersheds were modeled by the Soil and Water Assessment Tool (SWAT) under the shallow water‐table conditions, besides other analyses. The model was calibrated against 120 observed mean monthly flows (1995–2004) and validated for another 120 observations (2005–2014), with Nash–Sutcliffe efficiency (NSE) as the major performance assessment parameter. The model accurately simulated mean monthly flows for all watersheds during 1995–2014, except Winter River watershed (NSE = 0.02–0.33), wherein it overpredicted by 31%–52% and 5–12% in Wilmot River (NSE = 0.28–0.64). Streamflows were found highly dependent on groundwater; therefore, pumpings of 6.92 and 0.73 million cubic meters (MCM)/year caused the overpredictions in Winter and Wilmot watersheds, as SWAT cannot account pumping. In the rest three watersheds with negligible pumping, 4%–18% underprediction was due to multisite calibration. Spatially, streamflows randomly varied between 555 and 811 mm/year across watersheds, whereas thick and highly permeable sandstone produced higher recharges, the maximum ~600 mm/year in the eastern forest‐dominated Bear River watershed, lesser in western ~330 mm/year, and moderate ~450 mm/year in central watersheds. Temporally, March–May are the months of highest streamflows, whereas recharge is maximum during April–July. The succession trend justified strong surface water–groundwater interactions. Existing Water Extraction Permitting Policy ensures sustainability at the island scale. It sets pumping limit at 20% of recharge, that is, 0.48 km3/year altogether, against the present pumping of ~0.04 km3/year, yet a few watersheds are somewhat water‐stressed due to population and pumping concentration. Expansion of streamflow and groundwater monitoring, promoting population and pumping in rural areas, and more scrutiny for further pumping permits in water‐stressed watersheds are quite important for sustainable water management in PEI.

Occurrence of heatwave in Korea by the displacement of South Asian high

The South Asian high (SAH) index was defined using the 200 hPa geopotential height for 1973–2019. Of the movements of the SAH center in the north–south, east–west, northwest-southeast, and southwest-northeast directions, the movements in the northwest-southeast direction showed the highest positive correlation with heatwave days (HWDs) in South Korea. Thirteen years with the highest values in the northwestward shift of the SAH (positive SAH years) and 13 years with the highest values in the southeastward shift of the SAH (negative SAH years) were selected from a time series of SAH indices from which the linear trend was removed, and the differences between these two groups were analyzed. An analysis of vertical meridional circulation averaged along 120°–130° E showed that in the latitude zones containing Korea, anomalous downward flows with anomalous high pressures formed in the entire troposphere and coincided with a positive anomaly of air temperature and specific humidity. An analysis of stream flows and geopotential heights showed that in the positive SAH years, anomalous anticyclones developed in Korea, the North Pacific, North America, Western Europe, and the Iranian Plateau. These anticyclones had the wavenumber-5 pattern and showed more distinct barotropic vertical structures at higher altitudes, which resembled the circumglobal teleconnection (CGT) pattern. The maintenance of CGT depends on the interaction between the CGT circulation and the Indian summer monsoon (ISM), which has a major influence on the mid-latitude atmosphere. Strengthening of the ISM results in the formation of upper-level anomalous anticyclones in the northwestern Iranian Plateau and produces continuous downstream cells along the waveguide due to the Rossby wave dispersion. When diabatic heating by Indian summer monsoon precipitation is strengthened, the SAH is strengthened to the northwest of India, and a positive CGT pattern is formed. As a result, anomalous anticyclones formed in all layers of the Korean troposphere, resulting in heatwaves, tropical nights, and droughts exacerbated in South Korea.

Complexity analyses of Godavari and Krishna river streamflow using the concept of entropy

Complexity analyses of Godavari and Krishna river streamflow using the concept of entropy

Hydrologic flow regimes in humid tropics river basin.

The study is carried out to understand the impact of the land-use change in terms of alteration in flow regimes, which are understood to be a leading cause of ecological and environmental deterioration in riverine systems. Meenachil river in the humid tropical region of Kerala, India, is one of a kind river with human settlement along the banks for all its 78 kms of flow through the Kottayam District. The analysis of streamflow from four stream gauge stations was done using Range Variability Approach. The analysis was down as a two-time period analysis with the parametric approach with the period separation taken according to prior studies on land-use change. The analysis shows a high degree of alteration, which can be attributed to the land-use change and can be understood as the root cause for the deterioration of water quality and also the ecological distress, which is well documented in the downstream and watershed regions of the river.

A comprehensive calibration and validation of SWAT-T using local datasets, evapotranspiration and streamflow in a tropical montane cloud forest area with permeable substrate in central Veracruz, Mexico

Tropical montane cloud forests (TMCF) are threatened ecosystems despite their capacity to maintain high dry-season baseflow. A number of conservation policies, including payments for hydrological services, have been implemented to protect these forests. However, since most of the modeling tools used to assess the impacts of these policies were developed for temperate zones, more work is needed to understand and improve the applicability of popular models in tropical contexts. This study uses local evapotranspiration and streamflow datasets to calibrate and validate an improved version of the Soil and Water Assessment Tool model for the Tropics (SWAT-T). Vegetation growth and canopy water storage capacity were calibrated using field data. Three methods provided by SWAT-T to calculate potential evapotranspiration (PET) were compared: Penman-Monteith (SWAT-T-PM), Hargreaves (SWAT-T-HA), and Priestly-Taylor (SWAT-T-PT). Sensitivity analysis and calibration of daily streamflow were conducted at the catchment scale (34 km2). Furthermore, the calibrated models were validated at three sites with evapotranspiration data, and at four distinct micro-catchments (0.137–0.446 km2) with gauged streamflow data. Overall, SWAT-T satisfactorily simulated streamflow during the calibration period producing acceptable goodness of fit indices. However, the model incorrectly predicted the dominance of lateral flow instead of the deep groundwater flow observed from isotope-based studies. SWAT-T-HA performed better than SWAT-T-PM and SWAT-T-PT, but all models underestimated the influence of rainfall interception losses since evaporation is limited by daily PET in forests. Finally, SWAT-T largely over- and underestimated mean annual daily low flow in pastures and forests, respectively. Taken together, these results indicate that improvements in the parametrization of rainfall interception and deep subsurface flow dynamics in SWAT-T are required to improve applicability of this modeling tool in tropical montane areas underlain by permeable substrates.

Performance of HEC-HMS and SWAT to simulate streamflow in the sub-humid tropical Hemavathi catchment

Abstract The present study was conducted to examine the accuracy and applicability of the hydrological models Soil and Water Assessment Tool (SWAT) and Hydrologic Engineering Center (HEC)- Hydrologic Modeling System (HMS) to simulate streamflows. Models combined with the ArcGIS interface have been used for hydrological study in the humid tropical Hemavathi catchment (5,427 square kilometer). The critical focus of the streamflow analysis was to determine the efficiency of the models when the models were calibrated and optimized using observed flows in the simulation of streamflows. Daily weather gauge stations data were used as inputs for the models from the 2014–2020 period. Other data inputs required to run the models included land use/land cover (LU/LC) classes resulting from remote sensing satellite imagery, soil map and digital elevation model (DEM). For evaluating the model performance and calibration, daily stream discharge from the catchment outlet data were used. For the SWAT model calibration, available water holding capacity by soil (SOL_AWC), curve number (CN) and soil evaporation compensation factor (ESCO) are identified as the sensitive parameters. Initial abstraction (Ia) and lag time (Tlag) are the significant parameters identified for the HEC-HMS model calibration. The models were subsequently adjusted by autocalibration for 2014–2017 to minimize the variations in simulated and observed streamflow values at the catchment outlet (Akkihebbal). The hydrological models were validated for the 2018–2020 period by using the calibrated models. For evaluating the simulating daily streamflows during calibration and validation phases, performances of the models were conducted by using the Nash-Sutcliffe model efficiency (NSE) and coefficient of determination (R2). The SWAT model yielded high R2 and NSE values of 0.85 and 0.82 for daily streamflow comparisons for the catchment outlet at the validation time, suggesting that the SWAT model showed relatively good results compared to the HEC-HMS model. Also, under modified LU/LC and ungauged streamflow conditions, the calibrated models can be later used to simulate streamflows for future predictions. Overall, the SWAT model seems to have done well in streamflow analysis for hydrological studies.

Water allocation under climate change

Chile is positioned in the 20th rank of water availability per capita. Nonetheless, water security levels vary across the territory. Around 70% of the national population lives in arid and semiarid regions, where a persistent drought has been experienced over the last decade. This has led to water security problems including water shortages. The water allocation and trading system in Chile is based on a water use rights (WURs) market, with limited regulatory and supervisory mechanisms, where the volume to be granted as permanent and eventual WURs is calculated from statistical analyses of historical streamflow records if available, or from empirical estimations if they are not. This computation of WURs does not consider the nonstationarity of hydrological processes nor climatic projections. This study presents the first large sample diagnosis of water allocation system in Chile under climate change scenarios. This is based on novel anthropic intervention indices (IAI), which were computed as the ratio between the total granted water volume to the water availability within 87 basins in north-central and southern Chile (30°S–42°S). The IAI were evaluated for the historical period (1979–2019) and under modeled-based climatic projections (2055–2080). According to these IAI levels, to date, there are 20 out of 87 overallocated basins, which under the assumption that no further WURs will be granted in the future, increases up to 25 basins for the 2055–2080 period. The results show that, to date most of north-central Chilean catchments already have a large anthropic intervention degree, and the increases for the future period occurs mostly in the southern region of the country (approximately 38°S), which has been considered as possible source of water for large water transfer projects (i.e., water roads). These indices and diagnosis are proposed as a tool to help policy makers to address water scarcity under climate change.

A Review of SWAT Model Application in Africa

The soil and water assessment tool (SWAT) is a well-known hydrological modeling tool that has been applied in various hydrologic and environmental simulations. A total of 206 studies over a 15-year period (2005–2019) were identified from various peer-reviewed scientific journals listed on the SWAT website database, which is supported by the Centre for Agricultural and Rural Development (CARD). These studies were categorized into five areas, namely applications considering: water resources and streamflow, erosion and sedimentation, land-use management and agricultural-related contexts, climate-change contexts, and model parameterization and dataset inputs. Water resources studies were applied to understand hydrological processes and responses in various river basins. Land-use and agriculture-related context studies mainly analyzed impacts and mitigation measures on the environment and provided insights into better environmental management. Erosion and sedimentation studies using the SWAT model were done to quantify sediment yield and evaluate soil conservation measures. Climate-change context studies mainly demonstrated streamflow sensitivity to weather changes. The model parameterization studies highlighted parameter selection in streamflow analysis, model improvements, and basin scale calibrations. Dataset inputs mainly compared simulations with rain-gauge and global rainfall data sources. The challenges and advantages of the SWAT model’s applications, which range from data availability and prediction uncertainties to the model’s capability in various applications, are highlighted. Discussions on considerations for future simulations such as data sharing, and potential for better future analysis are also highlighted. Increased efforts in local data availability and a multidimensional approach in future simulations are recommended.

Water Allocation Efforts with Water Balance Analysis in the Jatiroto Sub-Watershed and Asem Sub Watershed, Lumajang Districts

Currently, water demand is increasing, both domestic, industrial and agricultural water needs. However, the increase in water demand is not due to an increase in the water availability due to changes in land use and other factors that pose a threat to increased exploitation of water resources. So it is necessary to analyze and evaluate the water needs to anticipate the impact of drought in the Asem-Tekung-Jatirowo sub watersheds. The calculation of water supply and water demand can be carried out using the water balance method, assisted by the WEAP (Evaporation and Water Planning) program, through data integration of streamflow analysis and water user in the river reach. The results showed that the sub-watershed area showed a deficit of water in 2013, with the Jatiroto region having the highest air deficit of 1.58 million m3 or 44.2%. Based on this analysis, urgently needed a recommendation of drought anticipation strategies these are planting patterns to adjust condition of water supply, storage of water reserves, conservation of critical land, and repair of channels that are at risk of water seepage.

A Unique Approach on How to Work Around the Common Uncertainties of Local Field Data in the PERSiST Hydrological Model

In the last two decades, the effects of global climate change have caused a continuous drying out of temperate landscapes. One way in which drying out has manifested is as a visible decrease in the streamflow in the water recipients. This article aims to answer the questions of how severe this streamflow decrease is and what is its main cause. The article is based on the analysis of daily streamflow, temperature, and precipitation data during five years (1 November 2014 to 31 October 2019) in a spruce-dominated temperate upland catchment located in the Czech Republic. Streamflow values were modeled in the PERSiST hydrological model using precipitation and temperature values obtained from the observational E-OBS gridded dataset and calibrated against in situ measured discharge. Our modeling exercise results show that the trend of decreasing water amounts in forest streams was very significant in the five-year study period, as shown in the example of the experimental catchment Křtiny, where it reached over −65%. This trend is most likely caused by increasing temperature. An unexpected disproportion was found in the ratio of increasing temperature to decreasing discharge during the growing seasons, which can be simplified to an increasing trend in the mean daily temperature of +1% per season, effectively causing a decreasing trend in the discharge of −10% per season regardless of the increasing precipitation during the period.

Assessment of four latest long-term satellite-based precipitation products in capturing the extreme precipitation and streamflow across a humid region of southern China

The lack of ground-based observation data usually limits the analysis of extreme precipitation and streamflow, especially for the ungauged or data-limited regions. Satellite-based precipitation products (SPPs) with high temporal and spatial resolutions can provide potential data sources in the regions without adequate precipitation data, and it has received much attention of regional or global hydro-climatic analysis. This study aims to evaluate the accuracy of four widely used long time series SPPs (CHIRPS, TMPA, CMORPH and PERSIANN) in capturing extreme precipitation and streamflow events in a humid region of southern China. It is found that, for extreme precipitation detection, both CMORPH and TMPA can capture most heavy and extreme precipitation, CMORPH works better on the rainfall distribution characteristics, while TMPA shows the best performance in capturing the extreme precipitation events with relatively low RMSE, ME and BIAS, and high R values of extreme precipitation indices. For the streamflow simulation, the combinations of different inputs and different models present different model performances. TMPA provides the most accurate hydrological model simulation results, while simulated streamflow forced by CMORPH exhibits considerable underestimation of streamflow. However, the combination of CMORPH and VIC model obtains the best efficiency for detecting extreme streamflow, followed by the combination of TMPA and SWAT model, which indicates the selection of a suitable model and input data is essential to obtain reliable and accurate results for the detection of extreme streamflow. This study is expected to provide a valuable reference for the application and comparison of multiple SPPs and models at watershed scales.

Spatial Analysis of Base Flow and Stream Flow from the Abbay River Basin after Watershed Management Interventions

Recently, increasing concern in Africa has been registered on the potential impacts on base flow and stream flow due to the implementation of watershed management interventions. This research incorporates spatially monthly geographical hydrological data sets into a developed spreadsheet water balance model to estimate the changes in surface runoff, base flow and stream flow as a result of implementing watershed management interventions in the Abbay River Basin during the period (2010-2018). The model was implemented at sub-catchment level. Considering Year 2005 as a datum for watershed management intervention, results of the modeling and spatial analysis indicated that watershed management interventions relatively reduced surface runoff, increased deep infiltration to groundwater and accordingly increased base flow to the stream. Among the key results in the Abbay Basin that change from Year 2010 to Year 2018 was reduction of surface runoff from the Abbay Basin in the amount of 1,753 million m3/yr. As a result, an increase in annual base flow in the amount of 23 million m3/yr was estimated, leaving a reduction in annual mean flow of the Abbay River in the amount of 1,731 million m3/yr of the Abbay River at El-Diem site. It is expected that the flow of the Abbay River will continue to decrease due to the continuous implementation of the watershed management interventions and agriculture expansion in the Abbay Basin.

Efficiency management in catch handling onboard small boats – Standardisation of processes in Icelandic fisheries

• Icelandic small boat fishers central to economic prosperity of remote communities. • Applied research methods used to develop exemplar standards for onboard catch handling. • Eight recommendations formed relating to safety, ergonomics, hygiene and fish handling. • Adoption of recommendations could lead to gains in time and resource efficiency. • Standardisation also likely to reap benefits in at least five Sustainable Development Goals. Small boat fishers are often the lifeblood of remote coastal communities in Iceland, contributing to employment, jobs and economic prosperity. This study conducts exploratory but highly practical research into the productive efficiency of onboard catch handling practices by Icelandic small boat fishers using fish handling tools called automatic jigging machines. Using applied research methods, this study researches whether standardisation of operations could be applied to make catch handling practices on small boats more time and resource efficient, leading to reduced waste, a consistently higher quality product, and potential increases in economic efficiency and sustainability. Thematic analysis, value stream mapping, flow analysis and Kaizen ideology were adopted to identify gaps and continuous improvement opportunities to standardise processes, leading to exemplary performance. Eight core recommendations are identified, seven of which are classed as straight-forward, ‘do now’ measures according to a Kaizen Priority Matrix. These include human and technological interventions in the areas of safety, organisational arrangements, hygiene, fish handling and bleeding, and cooling. Questionnaire responses reveal four main themes of importance to the sub-sector: changes in recent decades; the importance of small boat fishers; education and improvement; and the particularities of the sub-industry. The latter include the perception of a ‘race against time’ to land the catch, an issue that sometimes contributes to sub-optimal catch handling practices. Although this study has decidedly practical connotations for small boat fishers, its outcomes are also likely to be of interest to academics, particularly those focused on the organisational management of natural resources and general applications of the project management methodology and applied research methods as a means of solving practical problems in everyday life.

Mean Field Bias-Aware State Updating via Variational Assimilation of Streamflow into Distributed Hydrologic Models

When there exist catchment-wide biases in the distributed hydrologic model states, state updating based on streamflow assimilation at the catchment outlet tends to over- and under-adjust model states close to and away from the outlet, respectively. This is due to the greater sensitivity of the simulated outlet flow to the model states that are located more closely to the outlet in the hydraulic sense, and the subsequent overcompensation of the states in the more influential grid boxes to make up for the larger scale bias. In this work, we describe Mean Field Bias (MFB)-aware variational (VAR) assimilation, or MVAR, to address the above. MVAR performs bi-scale state updating of the distributed hydrologic model using streamflow observations in which MFB in the model states are first corrected at the catchment scale before the resulting states are adjusted at the grid box scale. We comparatively evaluate MVAR with conventional VAR based on streamflow assimilation into the distributed Sacramento Soil Moisture Accounting model for a headwater catchment. Compared to VAR, MVAR adjusts model states at remote cells by larger margins and reduces the Mean Squared Error of streamflow analysis by 2–8% at the outlet Tiff City, and by 1–10% at the interior location Lanagan.

Trends Analysis of Stream Flow at Different Gauging Stations in Upper Jhelum River

Analysis of stream flow trends plays a significant role in the flood forecasting and hydrologic drought assessment related investigations besides study of water resource management In this study, the long-term stream flow data recorded at different gauging stations in Upper Jhelum River (UJR) in Jammu and Kashmir (J &K) state basin were estimated using the Modified Mann-Kendall Test (MMKT) and Sen’s Slope Estimator (SSE).Long term time series data of ten gauging stations used for trend analysis were annual maximum and monthly maximum stream flows for the years (1980-2016) for the months of occurrence of flood in UJRB. It was observed that six gauging stations out of the ten showed a significant decreasing trend in discharge and depth of flow in the UJRB at 0.05 probability level of significance. However the results of the monthly and seasonal maximum stream flow analysis showed that during spring season (March to May) about 90% of the gauging stations depicted downward trends in the summer season (Jun to Aug) all the gauging stations showed downward stream flow trends and approximately 60% of the gauging stations showed downward trends in the month of September (first month of autumn). This analysis resulted into quantification of flood magnitudes and its periodicity of occurrences to develop flood mitigation strategies. Nonetheless, such investigation of water flow in the river would also assist in regional hydrologic studies besides occurrence of flood and hydrologic droughts.

The 2018 northern European hydrological drought and its drivers in a historical perspective

Abstract. In 2018, large parts of northern Europe were affected by an extreme drought. A better understanding of the characteristics and the large-scale atmospheric circulation driving such events is of high importance to enhance drought forecasting and mitigation. This paper examines the historical extremeness of the May–August 2018 meteorological situation and the accompanying meteorological and hydrological (streamflow and groundwater) drought. Further, it investigates the relation between the large-scale atmospheric circulation and summer streamflow in the Nordic region. In May and July 2018, record-breaking temperatures were observed in large parts of northern Europe associated with blocking systems centred over Fennoscandia and sea surface temperature anomalies of more than 3 ∘C in the Baltic Sea. Extreme meteorological drought, as indicated by the 3-month Standardized Precipitation Index (SPI3) and Standardized Precipitation Evapotranspiration Index (SPEI3), was observed in May and covered large parts of northern Europe by July. Streamflow drought in the Nordic region started to develop in June, and in July 68 % of the stations had record-low or near-record-low streamflow. Extreme streamflow conditions persisted in the southeastern part of the region throughout 2018. Many groundwater wells had record-low or near-record-low levels in July and August. However, extremeness in groundwater levels and (to a lesser degree) streamflow showed a diverse spatial pattern. This points to the role of local terrestrial processes in controlling the hydrological response to meteorological conditions. Composite analysis of low summer streamflow and 500 mbar geopotential height anomalies revealed two distinct patterns of summer streamflow variability: one in western and northern Norway and one in the rest of the region. Low summer streamflow in western and northern Norway was related to high-pressure systems centred over the Norwegian Sea. In the rest of the Nordic region, low summer streamflow was associated with a high-pressure system over the North Sea and a low-pressure system over Greenland and Russia, resembling the pattern of 2018. This study provides new insight into hydrometeorological aspects of the 2018 northern European drought and identifies large-scale atmospheric circulation patterns associated with summer streamflow drought in the Nordic region.

Evaluating the impact of climate change on stream flow: integrating GCM, hydraulic modelling and functional data analysis

Global climate change is an unequivocal reality that is immensely impacting the available water resources in many regions around the globe. For sustainable water resource management, the present research aims to evaluate the impact of climatic change on streamflow using both the global climate change and hydraulic models. This research presents a novel approach of applying functional data analysis (FDA) to highlight the commonalities and differences between the outcomes of various models for streamflow analysis. Observed temperature, precipitation and streamflow data from 1985 to 2014 of Astore catchment in the Upper Indus River Basin, in Pakistan, were used for this purpose. The precipitation and temperature results of three global climate models (GCMs) were obtained under two scenarios of greenhouse gas concentration, namely RCP 2.6 and RCP 8.5. Results of precipitation and temperature obtained under climate change scenarios were subsequently used to simulate the streamflow using the Hydrologic Engineering Centre-Hydraulic Modeling System (HEC-HMS). The FDA evaluated the Euclidean distances between the streamflow data predicted by various models. The diverging trend found in these distances identified some degree of dissimilarities in the streamflow results. The simulations manifest that the streamflow will increase in the study area (Astore) till 2070, while it is expected to decline in the distant future. The concerned agencies can adopt rational water resource management strategies based on the predicted streamflow in the region.

Assessing future socioeconomic drought events under a changing climate over the Pearl River basin in South China

Study regionPearl River basin (PRB) in South China. Study focusThis study aims to assess future socioeconomic drought events under a changing climate over the study region. Variable Infiltration Capacity (VIC) model is used to simulate the streamflow in the PRB during the period of 2020–2099, and 48 projected precipitation datasets from General Circulation Models (GCMs) are selected to drive the VIC model at 0.5° × 0.5° spatial resolution and daily temporal resolution. Then, the minimum in-stream water requirement (MIWR) of the PRB is determined, and trend analysis of the simulated streamflow is conducted. Socioeconomic drought index (SEDI) is used to detect the occurrence of socioeconomic drought event, and further, the impact of the reservoirs in the PRB on drought analysis is evaluated. New hydrological insights for the regionBased on any dataset, nearly one hundred socioeconomic drought events at different severity levels can be identified in the PRB; however, most of them, especially those at severe and extreme levels, can be mitigated through reservoir operation, i.e., reserving at least 40 % of the total manageable storage capacity (TMSC) in the reservoirs. Overall, this study can improve the recognition of future socioeconomic drought events, which is of great value for our society to effectively assess the impacts of climate change and water projects on sustainable water resources utilization in such river basins.

Phase State of Precipitation as a Factor of Low Flow in the Yana and Indigirka River Basins

The results of streamflow data analysis for 18 mountain catchments in the Yana and Indigirka river basins (1966–2015) with the area from 16.6 to 89600 km2 are presented. The average streamflow increased by 13 mm (54%) is September, by 1.5 mm (57%) in October, by 0.4 mm (59%) in November, and by 0.1 mm (80%) in December on 12, 11, 9, and 7 rivers, respectively. Basically, the streamflow variations are manifested in the form of abrupt shifts during 1991–1996. There is a decrease in precipitation in winter (by 8–13 mm) and the absence of significant changes in the other seasons. An increase in average annual air temperature by 2.0°C led to an increase in the amount of liquid precipitation and streamflow in September by about 12 mm. The revealed dependences of monthly streamflow on the amount of liquid precipitation in September for small catchments (as well as the single period (1991–1996), when the simultaneous variations in these hydrometeorological parameters are observed) indicate that the phase state of precipitation is the main factor of changes in the low flow for the analyzed rivers.