Water Storage Changes Research Articles

The Benefits of Continental-Scale High-Resolution Hydrological Modeling in the Detection of Extreme Hydrological Events in China

High-resolution hydrological modeling is crucial for detecting extreme hydrological events and understanding fundamental terrestrial processes. However, spatial resolutions in current hydrological modeling studies have been mostly constrained to relatively coarse resolution (~10–100 km), and they therefore have a difficult time addressing flooding or drought issues with fine resolutions. In this study, a continental-scale high-resolution hydrological modeling framework (0.0625°, ~6 km) driven by remote sensing products was used to detect extreme hydrological event occurrences in China and evaluated based on the Variable Infiltration Capacity (VIC) model. The results showed that the developed model provided more detailed information than the coarser resolution models (a 0.25° and 1°), thereby capturing the timing, duration, and spatial extent of extreme hydrologic events regarding the 2012 Beijing flood and 2009/10 drought in Hai River Basin. Here, the total water storage changes were calculated based on the VIC model (−0.017 mm/year) and Gravity Recovery and Climate Experiment (GRACE) satellite (−0.203 mm/year) to reflect the water availability caused by climate change and anthropogenic factors. This study found that the 0.0625° dataset could capture detailed changes, thereby providing reliable information during occurrences of extreme hydrological events. The high-resolution model integrated with remote sensing products could be used for accurate evaluations of continental-scale extreme hydrological events and can be valuable in understanding its long-term occurrence and water resource security.

Water and energy budgets over hydrological basins on short and long timescales

Abstract. Quantifying regional water and energy fluxes much more accurately from observations is essential for assessing the capability of climate and Earth system models and their ability to simulate future change. This study uses satellite observations to produce monthly flux estimates for each component of the terrestrial water and energy budget over selected large river basins from 2002 to 2013. Prior to optimisation, the water budget residuals vary between 1.5 % and 35 % precipitation by basin, and the magnitude of the imbalance between the net radiation and the corresponding turbulent heat fluxes ranges between 1 and 12 W m−2 in the long-term average. In order to further assess these imbalances, a flux-inferred surface storage (Sfi) is used for both water and energy, based on integrating the flux observations. This exposes mismatches in seasonal water storage in addition to important inter-annual variability between GRACE (Gravity Recovery and Climate Experiment) and the storage suggested by the other flux observations. Our optimisation ensures that the flux estimates are consistent with the total water storage changes from GRACE on short (monthly) and longer timescales, while also balancing a coupled long-term energy budget by using a sequential approach. All the flux adjustments made during the optimisation are small and within uncertainty estimates, using a χ2 test, and inter-annual variability from observations is retained. The optimisation also reduces formal uncertainties for individual flux components. When compared with results from the previous literature in basins such as the Mississippi, Congo, and Huang He rivers, our results show better agreement with GRACE variability and trends in each case.

Studying spatio-temporal patterns of vertical displacements caused by groundwater mass changes observed with GPS

The sensitivity of Global Positioning System (GPS) technique to detect displacements caused by Total Water Storage (TWS) changes has already been analyzed, while its sensitivity to individual TWS components, such as groundwater, is still in question. We use the probabilistic Principal Component Analysis (pPCA) to examine the spatio-temporal variations of vertical displacements from 98 GPS stations located in 9 regions of the world recognized as those where changes in groundwater masses are the most significant. To study the Earth's crust displacements induced by changes in groundwater masses, we remove from GPS displacements those induced by changes in masses of other water storage components using the WaterGAP Global Hydrology Model (WGHM). For validation purposes, displacements predicted by the Gravity Recovery and Climate Experiment (GRACE) missions from which the WGHM compartments other than groundwater are subtracted are also used. We estimate an average global trend of vertical displacements induced by groundwater mass changes equal to 0.4 ± 0.17 mm/yr for GRACE-WGHM differences. We observe that this trend is overestimated by groundwater-induced displacements estimated for GPS-WGHM differences for several regions around the world and mostly underestimated by WGHM. Spatio-temporal patterns are very coherent between GPS-WGHM differences and GRACE-WGHM differences with significant signatures observed for periods of intense natural and/or human-induced groundwater mass changes. We show that the determined GRACE-WGHM differences and GPS-WGHM differences capture most of the wet and dry periods reflected by the Standardized Precipitation Evapotranspiration Index (SPEI). We also find that groundwater-induced displacements estimated from the three datasets we use, show a prominent 6-year cycle. Finally, we demonstrate that GPS displacements can add very essential information to study and monitor local displacements due to groundwater mass changes and may successfully contribute to the climate-related research.

High-temporal-resolution monitoring of reservoir water storage of the Lancang-Mekong River

The Lancang-Mekong River (LMR) is an important transboundary river in Southeast Asia shared by China, Myanmar, Laos, Thailand, Cambodia, and Vietnam from upstream to downstream. Construction and operation of dams in the LMR basin has profoundly affected its natural streamflow regime. It is therefore important to monitor changes in reservoir water storage and to quantify the impact of reservoir operation on the redistribution of surface water resources over this basin. Given the difficulty in obtaining in-situ measurements of reservoirs on the LMR, we integrated multisource remote sensing, including satellite altimetry and optical and synthetic aperture radar (SAR) images, to generate weekly water levels and water storages of nine largest reservoirs on the main stem of the LMR from 2017 to 2021. Specifically, partial surface water extent (SWE) of reservoirs was extracted from Sentinel-1 SAR images and digital elevation models (DEMs), using Random Forest algorithms trained by partial SWE derived from Sentinel-2 optical images, showing an overall accuracy higher than 95%. Based on the partial SWE and water level estimates from ICESat-2 and Global Ecosystem Dynamics Investigation (GEDI, International Space Station-based) data, the relationships between water levels and partial SWE were derived to convert partial SWE into water level time series. Furthermore, water storage time series of the nine reservoirs were obtained from water level time series and hypsometric functions derived from SRTM DEMs that were corrected by ICESat-2 data to remove systematic errors. For the Xiaowan Reservoir on the Lancang River, there is close agreement between remote sensing-derived water levels and in-situ water levels in terms of a normalized RMSE lower than 5%. Results indicate that multisource remote sensing has large potential for high-temporal-resolution monitoring of reservoir water levels and water storage. This could more precisely evaluate impacts of cascade reservoirs on the streamflow of the LMR and facilitate drought and flood mitigation for riverine countries.

Long-Term Change of Lake Water Storage and Its Response to Climate Change for Typical Lakes in Arid Xinjiang, China

Lakes play a role as the sentinel of climate change. Surrounded by vast expanses of barren land with limited infrastructure, there is also a lack of knowledge about the dynamics of dryland lakes. The change of lake area can be effectively monitored by remote sensing, and multi-source satellite altimetry datasets provide the possibility to obtain long-term lake water level data. Using the Global Surface Water Monthly Historical dataset and altimetry water level dataset (Hydroweb), we reconstructed a time series of lake water storage changes in Xinjiang, Northwestern China, by establishing the empirical models based on the statistical relationship between the surface area and water level of each lake. We further explored lake response to climate change. The results show that the storage of water at Ayakkum Lake, Aqqikkol Lake and Aksayquin Lake have been undergoing an obvious expanding trend from 2000 to 2020, at a rate of 3.59×108m3/a, 9.43×108m3/a and 0.44×108m3/a, respectively. In the plain and transition zone, Ulungur Lake showed an upward tendency (0.413×108m3/a) in water storage, while Manas Lake and Bosten Lake experienced shrinkage with descending rates of −0.1×108m3/a and −0.86×108m3/a. Temperature changes significantly affect the lake water storage on plateaus, especially those lakes supplied with a large proportion of glacial meltwater. Precipitation is a key factor for changes of lake storage in the plain and transition zones. Meanwhile, extreme weather and man-made factors also play crucial roles. To reduce the risk of flood and drought disasters, rational regulation of water resources is required, and a large-scale integrated catchment management plan can avoid inadvertent trade-offs. This research provides a new perspective for lake water storage inversion, as well as data support for water resources management in arid areas including Xinjiang.

Precipitation changes and its interaction with terrestrial water storage determine water yield variability in the world's water towers

Previous studies have quantified the contributions of climate factors, vegetation, and terrestrial water storage change, and their interaction effects on hydrological process variation within the Budyko framework; however, further decomposition of the contributions of water storage change has not been systematically investigated. Therefore, focusing on the 76 water tower units of the world, the annual water yield variance was first examined, followed by the contributions of changes in climate, water storage change, and vegetation, as well as their interaction effects on water yield variance; finally, the contribution of water storage change on water yield variance was further decomposed into the effect of changes in groundwater, snow water, and soil water. The results showed that large variability exists in the annual water yield with standard deviations ranging from to 10–368 mm in water towers globally. The water yield variability was primarily controlled by the precipitation variance and its interacted effect with water storage change, with the mean contributions of 60 % and 22 %, respectively. Among the three components of water storage change, the variance in groundwater change had the largest effect on water yield variability (7 %). The improved method helps separate the contribution of water storage components to hydrological processes, and our results highlight that water storage changes should be considered for sustainable water resource management in water-tower regions.

Integrated ecohydrological hydrometric and stable water isotope data of a drought-sensitive mixed land use lowland catchment

Abstract. Data from long-term experimental catchments are the foundation of hydrological sciences and are crucial for benchmarking process understanding, observing trends and natural cycles, and being prerequisites for testing predictive models. Integrated data sets which capture all compartments of our landscapes are particularly important in times of land use and climate change. Here, we present ecohydrological data measured at multiple spatial scales which allow differentiation of “blue” water fluxes (which maintain streamflow generation and groundwater recharge) and “green” water fluxes (which sustain vegetation growth). There are two particular unique aspects to this data set: (a) we measured water stable isotopes in the different landscape compartments (i.e. in precipitation, surface water, soil, groundwater, and plant water), and (b) we conducted this monitoring during the extreme drought of 2018 in central Europe. Stable water isotopes are so useful in hydrology as they provide “fingerprints” of the pathways water took when moving through a catchment. Thus, isotopes allow one to evaluate the dynamic relationships between water storage changes and fluxes, which is fundamental to understanding how catchments respond to hydroclimate perturbations or abrupt land use conversion. Second, as we provide the data until 2020, one can also investigate recovery of water stores and fluxes after extreme droughts. Last but not least, lowland headwaters are often understudied systems despite them providing important ecosystem services such as groundwater and drinking water provision and management for forestry and agriculture. The data are available at https://doi.org/10.18728/igb-fred-826.3 (Dämpfling, 2023).

Responses of soil water dynamics to precipitation events in an alpine meadow ecosystem of the Qinghai Lake Basin based on high‐precision lysimeter measurements

AbstractIn high‐altitude cold areas, how precipitation and freeze–thaw processes affect soil water dynamics is not well understood due to a lack of high real‐time resolution measurements. This study measured soil water balance components with a high‐precision lysimeter in an alpine meadow ecosystem in the Qinghai Lake watershed from June 30, 2020, to June 30, 2021. The results showed that the total precipitation (TP), evapotranspiration (ET), soil water storage change (ΔS) and the vertical water flow (WF) of this ecosystem were 705.18, 633.21, 72.58 and −0.60 mm, respectively, during the study period. Continuous wet days with precipitation events larger than 10.00 mm led to percolation, while continuous dry days with strong ET caused an upward WF. Pearson correlation analysis suggests that a larger instantaneous precipitation intensity may be more conducive to an increase in shallow soil moisture (R2 > 0.72, p < 0.05). Furthermore, the TP thresholds in the complete thawing period inducing the soil water response in the mattic epipedon layer (0–20 cm) and organic layer (20–40 cm) were 3.24 mm and 16.61 mm, respectively. The difference in the average response time of soil water to a single precipitation event between the mattic epipedon layer and organic layer was 5.52 ± 3.65 h. These results deepen the understanding of the temporal pattern of water flux in alpine meadow ecosystems on the Tibetan Plateau.

Impacts of Water Resources Management on Land Water Storage in the Lower Lancang River Basin: Insights from Multi-Mission Earth Observations

Climate change and heavy reservoir regulation in the lower Lancang River basin (LLRB) have caused significant impacts on terrestrial water storage (TWS) in several ways, including changes in surface water storage (SWS), soil moisture storage (SMS), and groundwater storage (GWS). Understanding these impacts is crucial for promoting comprehensive cooperation in managing and utilizing water resources within the basin. This study utilized multi-mission Earth observation (EO) datasets, i.e., gravimetry (GRACE/-FO), altimetry (Jason-2, Sentinel-3, and Cryosat-2), imagery (Sentinel-1/2), and microwave sensors (IMERG), as well as gauged meteorological, hydrological data and reanalysis products, to investigate the spatial-temporal variation of water resources in the LLRB. The study shows that the fluctuations in precipitation and the construction of reservoirs are the primary drivers of changes in the TWS anomaly (TWSA) in the region. Precipitation decreased significantly from 2010 to 2019 (−34.68 cm/yr), but the TWSA showed a significant increase (8.96 cm/yr) due to enhanced water storage capacity in the Xiaowan and Nuozhadu reservoirs. SWS and GWS were also analyzed, with SWS showing a decrease (−5.48 cm/yr) from 2010 to 2019 due to declining precipitation and increasing evaporation. GWS exhibited a steady rise (9.73 cm/yr) due to the maintenance of groundwater levels by the reservoirs. This study provides valuable insights into the potential of EO data for monitoring water resources at a regional scale.

Global assessment of the sensitivity of water storage to hydroclimatic variations

Observing basin water storage response due to hydroclimatic fluxes and human water use provides valuable insight to the sensitivity of water storage to climate change. Quantifying basin water storage changes due to climate and human water use is critical for water management yet remains a challenge globally. Observations from the Gravity Recovery and Climate Experiment (GRACE) mission are used to extract monthly available water (AW), representing the combined storage changes from groundwater and surface water stores. AW is combined with hydroclimatic fluxes, including precipitation (P) and evapotranspiration (ET) to quantify the hydroclimatic elasticity of AW for global basins. Our results detect consequential global water sensitivity to changes in hydroclimatic fluxes, where 25 % of land areas exhibit hydroclimatic elasticity of AW >10, implying that a 1 % change in monthly P-ET would result in a 10 % change in AW. Corroboration using a Budyko-derived metric substantiates our findings, demonstrating that basin water storage resilience to short-term water deficits is linked to basin partitioning predictability, and uniform seasonality of hydroclimatic fluxes. Our study demonstrates how small shifts in hydroclimate flux may affect available water storage potentially impacting billions globally.

Divergent spatiotemporal variability of terrestrial water storage and eight hydroclimatic components over three different scales of the Yangtze River basin

Terrestrial water storage anomaly (TWSA) from Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on was first exacted by using the forward modeling (FM) method at three different scales over the Yangtze River basin (YRB): whole basin, three middle sub-basins, and eleven small sub-basins (total 15 basins). The spatiotemporal variability of eight hydroclimatic variables, snow water storage change (SnWS), canopy water storage change (CnWS), surface water storage anomaly (SWSA), soil moisture storage anomaly (SMSA), groundwater storage anomaly (GWSA), precipitation (P), evapotranspiration (ET), and runoff (R), and their contribution to TWSA were comprehensively investigated over the YRB. The results showed that the root mean square error of TWS change after FM improved by 17 %, as validated by in situ P, ET, and R data. The seasonal, inter-annual, and trend revealed that TWSA over the YRB increased during 2003–2018. The seasonal TWSA signal increased from the lower to the upper of YRB, but the trend, sub-seasonal, and inter-annual signals receded from the lower to the upper of YRB. The contribution of CnWS to TWSA was small over the YRB. The contribution of SnWS to TWSA occurs mainly in the upper of YRB. The main contributors to TWSA were SMSA (~36 %), SWSA (~33 %), and GWSA (~30 %). GWSA can be affected by TWSA, but other hydrological elements may have a slight impact on groundwater in the YRB. The primary driver of TWSA over the YRB was P (~46 %), followed by ET and R (both ~27 %). The contribution of SMSA, SWSA, and P to TWSA increased from the upper to the lower of YRB. R was the key driver of TWSA in the lower of YRB. The proposed approaches and results of this study can provide valuable new insights for water resource management in the YRB and can be applied globally.

A Bibliometric and Visualized Analysis of Remote Sensing Methods for Glacier Mass Balance Research

In recent decades, climate change has led to global warming, glacier melting, glacial lake outbursts, sea level rising, and more extreme weather, and has seriously affected human life. Remote sensing technology has advanced quickly, and it offers effective observation techniques for studying and monitoring glaciers. In order to clarify the stage of research development, research hotspots, research frontiers, and limitations and challenges in glacier mass balance based on remote sensing technology, we used the tools of bibliometrics and data visualization to analyze 4817 works of literature related to glacier mass balance based on remote sensing technology from 1990 to 2021 in the Web of Science database. The results showed that (1) China and the United States are the major countries in the study of glacier mass balance based on remote sensing technology. (2) The Chinese Academy of Sciences is the most productive research institution. (3) Current research hotspots focus on “Climate change”, “Inventory”, “Dynamics”, “Model”, “Retreat”, “Glacier mass balance”, “Sea level”, “Radar”, “Volume change”, “Surface velocity”, “Glacier mapping”, “Hazard”, and other keywords. (4) The current research frontiers include water storage change, artificial intelligence, High Mountain Asia (HMA), photogrammetry, debris cover, geodetic method, area change, glacier volume, classification, satellite gravimetry, grounding line retreat, risk assessment, lake outburst flood, glacier elevation change, digital elevation model, geodetic mass balance, (DEM) generation, etc. According to the results of the visual analysis of the literature, we introduced the three commonly used methods of glacier mass balance based on remote sensing observation and summarized the research status and shortcomings of different methods in glacier mass balance. We considered that the future research trend is to improve the spatial and temporal resolution of data and combine a variety of methods and data to achieve high precision and long-term monitoring of glacier mass changes and improve the consistency of results. This research summarizes the study of glacier mass balance using remote sensing, which will provide valuable information for future research across this field.

Satellite gravity observation and hydrological modelling-based integrated groundwater storage change in Northwestern India

Abstract This paper presents a novel approach for an improved estimate of regional groundwater storage (GWS) change in Northwestern India by integrating satellite-based Gravity Recovery and Climate Exchange (GRACE) gravity observation and hydrological modelling of satellite/in situ hydrometeorological data. Initially, GRACE observation-based terrestrial water storage (TWS) change and hydrological model-based TWS change products were integrated using weight coefficients derived from multi-linear regression analysis of TWS change vs governing hydrological components. Later, the monthly average soil moisture change was subtracted from the monthly average individual and integrated TWS change products to obtain GWS change products. By spatial correlation analysis, three GWS change products were then compared with groundwater level (GWL) fluctuation-based in situ GWS change. Hydrological model, spaceborne GRACE observation, and integrated GWS change products show a positive correlation in ∼59, ∼69, and ∼73% of the area with in situ GWS change. While a hydrological model-based estimate considers geology, terrain, and hydrometeorological conditions, GRACE gravity observation includes groundwater withdrawal from aquifers. All the factors are included in the integrated product. The approach overcomes the limitations of GRACE observation (spatial resolution, geology, terrain, and hydrometeorological factors), hydrological modelling (groundwater withdrawal conditions), and conventional GWL fluctuation-based method (inadequate spatial continuity and cumbersome, labour-intensive exercise).

Assimilation of GRACE Follow‐On Inter‐Satellite Laser Ranging Measurements Into Land Surface Models

AbstractThe monthly mean level‐2 (L2) time‐variable gravity as well as level‐3 (L3) Mass Concentration blocks (mascons) data from Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow‐On (GRACE‐FO) missions are frequently used for improving land surface models. The conventional data assimilation approach requires several pre‐processing steps like filtering (to suppress the random and systematic errors), correction (to reduce the leakage effect) and scaling (to un‐do the attenuation effect by filters) before integrating the data with the models, for example, when computing total water storage (TWS) changes from L2 data. Moreover, due to the monthly sampling of L2 and L3 data, the model estimates are updated only once a month. This confines the applications of the approaches to cases where water storage is slowly varying at seasonal or interannual time‐scales. We present a new methodology based on direct assimilation of along‐orbit Line‐of‐sight Gravity Difference (LGD) measurements from the GRACE‐FO laser ranging interferometer (LRI) which overcomes the limitation of the conventional approach. Inter‐satellite ranging data reflect the gravitational changes at satellite altitude caused by the instantaneous TWS changes at the Earth surface. Therefore, they pose information at wide‐ranging time‐scales from hours to multiple years. The proposed method is applied globally to assimilate LRI data into a land surface model. Evaluation against multiple satellite‐based and ground data shows the superiority of our proposed approach. The new approach also offers better performance in capturing high‐frequency water storage variations imposed by sub‐monthly climatic events due to its higher number of data assimilation cycles within a month.

Methods for Estimating Surface Water Storage Changes and Their Evaluations

Abstract Developing effective methods for estimating regional-scale surface water storage change (ΔSW) has become increasingly important for water resources studies and environmental impact assessment. Three methods for estimating monthly ΔSW are proposed in this study, of which one is based on land surface runoff and two that use water body water budgets. Water areas observed by Landsat satellites for Canada’s entire landmass are used for evaluation of the results. The surface runoff method achieved the least satisfactory results, with large errors in the cold season or dry regions. The two water-budget methods demonstrated significant improvements, particularly when water area dynamics is considered in the estimation of the water body water budget. The three methods performed consistently across different climate regions in the country and showed better correlations with observations over wet climate regions than over dry regions with poorly connected hydrological system. The results also showed the impact of glacier and permanent snow melts over the Rocky Mountains on basin-scale surface water dynamics. The methods and outputs from this study can be used for calibrating and validating hydrological and climate models, assessing climate change and human disturbance impacts on regional water resources, and filling the ΔSW data gaps in GRACE-based total water storage decompositions studies. Significance Statement The purpose of this study is to develop and evaluate methods for estimating regional-scale surface water storage change. This is important because information on surface water dynamics is limited for water resources studies and environmental impact assessment. Our study makes available two new methods which significantly improve on surface water storage estimation from the traditional runoff model. A guide on controls of surface water dynamics is provided for regions under various hydroclimate and physiographic–hydraulic conditions and reveals the influence of glacier melt on surface water variations.

Contribution of vanishing mountain glaciers to global and regional terrestrial water storage changes

Mountain is called the water towers of the world. Due to high sensitivity and vulnerability to climate change, more attention is paid to the change of water resources in mountain regions, where provide water for environmental and human demands downstream. Mountains glacier, as one of the most important components of terrestrial water storage (TWS), effectively regulates and stabilizes surface water resources. TWS appears to be trending below previous ranges in recent years, and glacier retreating is becoming the primary cause of TWS depletion in mountain regions. However, how much mountain glacier changes contribute to TWS changes around mountain regions is unknown. Here, we combine multi-source datasets to quantify the contribution rate over high-elevation mountain regions. On a global scale, the glacial melting is equivalent to about 49% of the total TWS decline during 2006–2015. TWS and glacier show decreasing trends in most of mountain regions and watersheds of the Third Pole and surroundings (TPs), but the contribution ranges from −23% to 728% in mountain regions and −21% to 99% in watersheds of TPs. There are larger contributions in regions with more glaciers, while smaller in less glacier-covered regions. Glacier together with other storage components play diverse roles across different mountain regions and watersheds, but factors with great influence are glacier, groundwater, soil water, reservoirs and lakes.

Satellite observation of atmospheric CO2 and water storage change over Iran

Like many other Middle East countries, Iran has been suffering from severe water shortages over the last two decades, as evidenced by significant decline in surface water and groundwater levels. The observed changes in water storage can be attributed to the mutually reinforcing effects of human activities, climatic variability, and of course the climate change. The objective of this study is to analyze the dependency of atmospheric CO2 increase on the water shortage of Iran, for which we investigate the spatial relationship between water storage change and CO2 concentration using large scale satellite data. We conduct our analysis using water storage change data from GRACE satellite and atmospheric CO2 concentration from GOSAT and SCIAMACHY satellites during 2002–2015. To analyze the long-term behavior of time series we benefit from Mann-Kendal test and for the investigation of the relationship between atmospheric CO2 concentration and total water storage we use Canonical Correlation Analysis (CCA) and Regression model. Our Results show that the water storage change anomaly and CO2 concentration are negatively correlated especially in northern, western, southwest (Khuzestan province), and also southeast (Kerman, Hormozgan, Sistan, and Baluchestan provinces) of Iran. CCA results reveal that in the most of northern regions, the decrease in water storage is significantly influenced by the increase of CO2 concentration. The results further show that precipitation in the highland and peaks does not seem to be influenced by the long and short-term variation in CO2 concentration. Besides, our results show that the CO2 concentration is slightly correlated with a weak positive trend in evapotranspiration over agricultural areas. Thus, the indirect effect of CO2 on increasing evapotranspiration is observed spatially in the whole of Iran. The results of the regression model between total water storage change and carbon dioxide (R2 = 0.91)/water discharge/water consumption show that carbon dioxide has the highest effect on total water storage change at large scale. The results of this study will contribute to both water resource management and mitigation plans to achieve the goal of CO2 emission reduction.

Climatic and different human influences on annual and seasonal streamflow with considering the soil water storage change in the middle reaches of the Yellow River basin, China

Recent climate change and more intensive human activities have induced significant changes in streamflow along the middle reaches of the Yellow River basin (MRYRB), which has attracted considerable attention from the scientific community. However, most previous studies have focused on changes in annual streamflow by examining data from a small number of hydrological stations and the role of the various human activities remains unclear. Here we used an extended Budyko-based framework that considered changes in soil water storage (ΔS) to determine the contributions of changes in streamflow, both at the annual and seasonal scale. These analysis were conducted on 40 catchments and three sections (Toudaoguai–Longmen, TDG–LM; Longmen-Huayuankou, LM–HYK; and Toudaoguai–Huayuankou, TDG–HYK) in the MRYRB from 1971 to 2015. Results showed that streamflow at most catchments and sections declined dramatically after years of abrupt change detected by the Pettitt test, with decreases occurring at a faster rate during flood seasons (42.9%) than during non-flood seasons (31.8%). Although human behaviors were often the main cause of streamflow reductions at the annual and seasonal scales, the effects of ΔS became more important at increasingly finer scales. Indeed, they were of equal or greater importance than human impacts in some catchments, with corresponding relative contributions up to 48%. The effects of human activities may possibly have been overestimated or underestimated by 1–16% in three sections when the impact of ΔS was not considered. Further analysis indicated that human water use – particularly the rapid increase in water withdrawals for domestic purposes, electricity generation, and manufacturing – was the primary factor among human activities that affected streamflow reduction in the LM–HYK and TDG–HYK sections at different timescales, comprising 60–90% of all impacts. By contrast, the effects of water use and other human factors were almost equal in the TDG–LM section. Among the other human factors, vegetation restoration played a more critical role in the TDG–LM section, whereas the construction of check-dams was more important in the LM–HYK section. These findings of our study can enhance the understanding of hydrological changes in response to environmental factors.

Comment on “Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina” by Halla et al. (2021)

Abstract. Recently published work on water preservation in Chile assumes that “permafrost” (cryogenic) rock glaciers are dominant. Melt pond development shows that rock glaciers are glacier-derived (“glacigenic”) rather than of permafrost origin.

Continuous Intra-Annual Changes of Lake Water Level and Water Storage from 2000 to 2018 on the Tibetan Plateau

There is a large amount of lakes on the Tibetan Plateau (TP), which are very sensitive to climate change. Understanding the characteristics and driving mechanisms of lake change are crucial for understanding climate change and the effective use of water resources. Previous studies have mainly focused on inter-annual lake variation, but the continuous and long-term intra-annual variation of lakes on the TP remains unclear. To address this gap, we used the global surface water (GSW) dataset and the Shuttle Radar Topography Mission (SRTM) DEM to estimate the water level and storage changes on the TP. The results indicated that the average annual minimum lake water level (LWLmin) and the average annual maximum lake water level (LWLmax) increased by 3.09 ± 0.18 m (0.16 ± 0.01 m/yr) and 3.69 ± 0.12 m (0.19 ± 0.01 m/yr) from 2000 to 2018, respectively, and the largest change of LWLmin and LWLmax occurred in 2002–2003 (0.45 m) and 2001–2002 (0.39 m), respectively. Meanwhile, the annual minimum lake water storage change (LWSCmin) and annual maximum lake water storage change (LWSCmax) were 125.34 ± 6.79 Gt (6.60 ± 0.36 Gt/yr) and 158.07 ± 4.52 Gt (8.32 ± 0.24 Gt/yr) from 2000 to 2018, and the largest changes of LWSCmin and LWSCmax occurred in the periods of 2002–2003 (17.67 Gt) and 2015–2016 (17.51 Gt), respectively. The average intra-year changes of lake water level (LWLCintra-year) and the average intra-year changes of lake water storage (LWSCintra-year) were 0.98 ± 0.23 m and 40.19 ± 10.67 Gt, respectively, and the largest change in both LWLCintra-year (1.44 m) and LWSCintra-year (62.46 Gt) occurred in 2018. The overall trend of lakes on the TP was that of expansion, where the LWLC and LWSC in the central and northern parts of the TP was much faster than that in other regions, while the lakes in the southern part of the TP were shrinking, with decreasing LWLC and LWSC. Increased precipitation was found to be the primary meteorological factor affecting lake expansion, and while increasing glacial meltwater also had an important influence on the LWSC, the variation of evaporation only had a little influence on lake change.