Regional Water Balance Research Articles

Soil database development with the application of machine learning methods in soil properties prediction

Excessive rainwater infiltration can be an important causal agent of both slope and whole tree uprooting failures. Early warnings or stabilization measures on high-risk slopes or trees are critically important. To identify the high-risk areas, it is necessary to conduct seepage, slope and tree stability analyses over a large region. Given the spatial variability of soil properties, a soil database is therefore required before performing distributed or Geographical Information System (GIS) -based water balance and stability analyses. Considering that the unsaturated soil properties could be very different from saturated soil properties, in this study, a soil database containing both saturated and unsaturated hydraulic and mechanical soil properties was developed for the first time. Machine learning methods were used to predict the unknown soil properties. Based on the predicted soil properties, spatial distributions of different saturated and unsaturated soil properties were generated using the ordinary kriging method. Then the soil database was developed with Singapore island being divided into 97 zones, with each zone having similar soil properties. In this study, the importance of different input variables in soil properties prediction was also investigated. In addition to soil plasticity (i.e., Liquid Limit (LL), Plastic Limit (PL) and Plasticity Index (PI)) and grain size distribution (i.e., gravel, sand, and fines fractions), location (i.e., longitude and latitude) was found to be of high importance as well and are recommended to be used as input variables to predict soil properties, especially when data volume is relatively limited. For those soil properties that cover a large range of values, model performance is better when logarithm values were used as the outputs. Moreover, given the possible correlation between some output parameters, the prediction of the Soil-water Characteristic Curve (SWCC) from a multi-output model is recommended after comparing its performance with a single output model. Furthermore, the performance of two commonly used machine learning methods (i.e., random forest regression and artificial neural network) in soil properties prediction were compared and the prediction error resulting from the random forest regression method was generally smaller. The developed database includes the mean values of saturated permeability, saturated and unsaturated shear strength parameters, and SWCC in each zone. The database can be applied in regional GIS-based water balance and slope stability analyses to account for the spatial heterogeneity instead of assuming constant soil properties.

Development of the regional water balance regulation concept based on the geosystem approach

The article is devoted to solving the scientific problem of the regional water balance regulation concept development. The authors have proposed a methodology for solving the problem of the scarcity of labeled spatial data, based on the geosystem approach. A deep neural network model for the analysis of the geosystem model of the territory is proposed. An approach to the formation of ensembles of classifiers to improve the accuracy of the classification of spatial data is described. It is proved that the hierarchical structuring of geosystems optimizes diagnostics of the leading agents of physical and geographical factors interaction, patterns of spatio-temporal changes in their states, direction of metabolic processes and transformation of matter and energy development. Studies have shown that the combination of factors variety in the water balance formation forms many types of water resources conditions formation.

Estimation of regional farmland irrigation water requirements and water balance in Northeast China.

Agricultural water use has long accounted for more than 70% of water consumption in Northeast China. Estimating farmland irrigation water requirements and water balance is essential to ensure safe agricultural water and promote rational development and utilization of regional water resources. In this study, based on the modified Penman-Monteith equation recommended by the Food and Agriculture Organization (FAO) and Geographic Information System (GIS) technology, the net crop irrigation water requirements for four main crops in Northeast China were calculated, and the spatiotemporal distribution characteristics were also analyzed. Additionally, regional farmland irrigation water requirements were estimated, water balance in a typical year was determined, and the dominant factors affecting farmland irrigation water requirements in different regions were analyzed. From 1986 to 2020, the net irrigation water requirements for four main crops all showed the temporal trend of no significant increase and the spatial distribution characteristic of being high in the west and low in the east. The farmland irrigation water requirement decreased, and the monthly average farmland irrigation water requirement peaked in July during 2010-2019. Compared with 2010, in 2019, the irrigation water requirement per cultivated land grid cell in 20 cities increased and that in 16 cities decreased. Most cities were facing varying degrees of water shortage. Precipitation had the greatest direct effect on the farmland irrigation water requirement in different regions. These results quantify the farmland irrigation water requirement and water balance in Northeast China, and provide a reference for water resources and related environmental governance.

Assessing and delineation of groundwater recharge areas in coastal arid area southern Tunisia

In Gabès region (southeastern Tunisia), given the semi-arid to arid climate conditions, groundwater is an essential resource to supply the growth needs of the socio-economic development. To ensure sustainable development and preserve water resources, a careful estimation of the present day recharge amount and the delineation of the potential zones of rainfall precipitation are of required for an accurate evaluation of regional water balance. In this context, this study aims to a preliminary assessment of groundwater recharge in Gabes basin in regard to the delineation of the potential recharge areas of phreatic aquifers. Thus, a geological and hydrogeological collected database coupled with remote sensing techniques (RST) were used for the determination of the lateral variation of recharging zone, Treatment by ArcGIS and Matlab softwares and Kohonen self-organizing maps (K-SOM) approaches. The obtained results indicate that five recharge potential areas have been identified and classified as 27% very low, 23% low, 40% moderate recharge, 7% good and 3% very good potential recharge located principally on southern part of the study region. This distribution is controlled principally by the geomorphological, geologic, and hydrogeologic features of the region. Reasonable management strategies based on a perennial exploitation of these low renewable resources are required to optimize the water dependent socio-economic development. The estimated groundwater potential recharge of Gabès aquifer system using K-SOM and RST is of 11.4 Mm3 y−1. This recharging rate is very low it present 7% of the total rain, thus it must be ameliorated. K-SOM and RST approach is a useful method for groundwater potential recharge mapping and is a helpful of wells establishment and groundwater sustainable management. an isotopic analyses is recommended to ameliorate the decision maker to establish the adequate strategy.

Modeling the Hydrologic Influence of Subsurface Tile Drainage Using the National Water Model

AbstractSubsurface tile drainage (TD) is a dominant agriculture water management practice in the United States (US) to enhance crop production in poorly drained soils. Assessments of field‐level or watershed‐level (<50 km2) hydrologic impacts of TD are becoming common; however, a major gap exists in our understanding of regional (>105 km2) impacts of TD on hydrology. The National Water Model (NWM) is a distributed 1‐km resolution hydrological model designed to provide accurate streamflow forecasts at 2.7 million reaches across the US. The current NWM lacks TD representation which adds considerable uncertainty to streamflow forecasts in heavily tile‐drained areas. In this study, we quantify the performance of the NWM with a newly incorporated tile‐drainage scheme over the heavily tile‐drained Midwestern US. Employing a TD scheme enhanced the uncalibrated NWM performance by about 20–50% of the fully calibrated NWM (Calib). The calibrated NWM with tile drainage (CalibTD) showed enhanced accuracy with higher event hit rates and lower false alarm rates than Calib. CalibTD showed better performance in high‐flow estimations as TD increased streamflow peaks (14%), volume (2.3%), and baseflow (11%). Regional water balance analysis indicated that TD significantly reduced surface runoff (−7% to −29%), groundwater recharge (−43% to −50%), evapotranspiration (−7% to −13%), and soil moisture content (−2% to −3%). However, TD significantly increased soil profile lateral flow (27.7%) along with infiltration and soil water storage potential. Overall, our findings highlight the importance of incorporating the TD process into the operational configuration of the NWM.

Do Ecological Restoration Projects Improve Water-Related Ecosystem Services? Evidence from a Study in the Hengduan Mountain Region.

Land use/land cover (LULC) and climate change are major driving forces that impact ecosystem services and affect human well-being directly and indirectly. Under the future interaction between LULC and climate change, the impact of different land management and climate change scenarios on water-related services is uncertain. Based on this, the CLUMondo model, which focuses on land use intensity, was used to simulate the land system under different land management scenarios in the future. By coupling the downscaled climate scenario data, this study used the InVEST and RUSLE models to estimate the annual water yield and soil erosion in 2050 in the Hengduan Mountain region and analyzed the variation differences in different sub-watersheds. The results indicated that, under the influence of LULC and climate change, when compared with the amount for 2020, the soil erosion in the Hengduan Mountain region in 2050 was reduced by 1.83, 3.40, and 2.91% under the TREND scenario, FOREST scenario, and CONSERVATION scenario, respectively, while the water yield decreased by 5.05, 5.37, and 5.21%, respectively. Moreover, the change in soil erosion in the study area was affected by precipitation and closely related to the precipitation intensity, and the impact of climate change on the water yield was significantly greater than that of LULC change. The spatial heterogeneity of soil erosion and water yield was obvious at the sub-watershed scale. In the future, soil erosion control should be strengthened in the northern regions, while water resource monitoring and early warning should be emphasized in the central-eastern regions. Our results provide scientific guidance for policy makers to formulate better LULC policies to achieve regional water and soil balance and sustainable management.

Suitability Evaluation of Cultivated Land Reserved Resources in Arid Areas Based on Regional Water Balance

Suitability Evaluation of Cultivated Land Reserved Resources in Arid Areas Based on Regional Water Balance

A Late Holocene Stable Isotope and Carbon Accumulation Record from Teringi Bog in Southern Estonia

Radiocarbon-dated peat cores collected from an ombrotrophic bog in southern Estonia record shifting environmental conditions and carbon accumulation rates in northern Europe during the late Holocene. Modern observations indicate that the water balance of the peatland is highly influenced by changes in relative humidity, followed by temperature and precipitation. The modern δ18O and δ2H values of surface water suggest that the groundwater is an integration of several months of precipitation. There also appears to be little or no direct influence of surface evaporation on the water within the bog, suggesting that water loss is preferentially through transpiration and sub-surface flow. Bulk peat δ13C values exhibit a trend of higher values through the late Holocene, suggesting a pattern of overall increased surface wetness. The δ15N values were low from ~4130 to 3645 cal yr BP, suggesting drier conditions, followed by intermediate values until ~2995 cal yr BP. The δ15N values decrease again from ~2995 to 2470 cal yr BP, suggesting a return to drier conditions, followed by intermediate values until ~955 cal yr BP. The δ15N values were high, suggesting wetter conditions from ~955 to 250 cal yr BP, followed by intermediate values through the modern. Carbon accumulation rates were low to intermediate from ~4200 to 2470 cal yr BP, followed by intermediate-to-high values until ~1645 cal yr BP. Carbon accumulation rates were then low until ~585 cal yr BP, followed by intermediate values through the modern. The geochemical data, combined with observed changes in peat composition and regional proxies of temperature and water table fluctuations through the late Holocene, suggest that carbon accumulation rates were relatively low under dry and warm conditions, whereas accumulation was generally higher (up to ~80 g C m−2 yr−1) when the climate was wetter and/or colder. These findings further suggest that future environmental changes affecting the regional water balance and temperature will impact the potential for northern peatlands to capture and store carbon.

On the attribution of changing water surface evaporation across China

Study regionChina Study focusWater evaporation represents a pivotal indicator of the terrestrial ecosystem and hydrological cycle, influencing regional water and energy balance to some extent. In this study, the long-term data series of water surface evaporation (Ep) were assimilated across China, with the observations from 552 national benchmark weather stations. The trends of Ep and the influential climate variables were well detected. The analytical derivation method was built up to quantitatively attribute the effects from 5 key climate fields to Ep variations, including wind speed (u2), sunshine duration (n), relative humidity (RH), daily maximum (Tmax), and minimum (Tmin) air temperature. New hydrological insights for the regionThe attribution results were more accurate and reasonable than those from two commonly used statistically based climate elasticity methods, which tended to overestimated the Ep variations. Most weather stations had experienced the decreasing trends of Ep during the entire research period of 1961–2018, which were mainly attributed to the decreasing in u2, n and RH, while the effects of regional warming (rising air temperature) were less influential on Ep variations at the long-term scale. The variations of Ep attributed to the three main influential climate variables (u2, n and RH) across China had also shown different temporal and spatial tendency patterns during different historical research periods. For example, the changing n and RH had shown increasing power on Ep variations in the western China climate zones. Comparatively, the u2 has been losing its power in decreasing Ep in most regions of China due to the slowdown in the declining rates of wind speed. This dynamic Ep attribution process is worthy of continuous focus and systematic research.

Impacts of Climatic Variation and Human Activity on Runoff in Western China

Hydrological cycle is sensitively affected by climatic variation and human activity. Taking the upper- and middle-stream of the Weihe River in western China as an example, using multiple meteorological and hydrological elements, as well as land-use/land-cover change (LUCC) data, we constructed a sensitivity model of runoff to climatic elements and human activities based on the hydro-thermal coupling equilibrium equation, while a cumulative slope was used to establish a comprehensive estimation model for the contributions of climatic variation and human activities to the changes of runoff. The results showed that the above function model established could be well applied to quantitatively study the elasticity of runoff’s response to climatic variation and human activities. It was found that the annual average precipitation, evaporation, wind velocity, sunshine hours, relative humidity and runoff showed decreasing trends and that temperature increased. While in the hydrological cycle, precipitation and relative humidity had a non-linear positive driving effect on runoff, while temperature, evaporation, sunshine hours, wind velocity, and land-use/land-cover change (LUCC) have non-linearly negatively driven the variation of runoff. Moreover, runoff has a strong sensitive response to precipitation, evaporation and LUCC. In areas with strong human activities, the sensitivity of runoff to climatic change was decreasing, and runoff has a greater elastic response to underlying surface parameters. In addition, the analysis showed that the abrupt years of climate and runoff changes in the Weihe River Basin were 1970, 1985 and 1993. Before 1985, the contribution rate of climatic variation to runoff was 68.3%, being greater than that of human activities to runoff, and then the contribution rates of human activities to runoff reached 75.1%. The impact of natural climate on runoff was weakened, and the effect of human activities on runoff reduction increased. Under 30 hypothetical climatic scenarios, the evaluation of runoff in the future showed that the runoff in the Weihe River Basin will be greatly reduced, and the reduction will be more significant during the flood season. Comparing the geographically fragile environments and intense human activities, it was believed that climatic variation had a dramatic effect on driving the water cycle of precipitation and evaporation and affected regional water balance and water distribution, while human activities had driven the hydrological processes of the underlying surface, thus becoming the main factors in the reduction of runoff. This study provided scientific tools for regional climate change and water resources assessment.

Climate change as an environmental threat on the central plains of the Carpathian basin based on regional water balances

Climate change is an essential environmental challenge nowadays. Its effects are already being felt in multiple ways. In the future, we will also have to adapt to its effects because of our farming and our daily lives. In our research, we assessed the climate sensitivity of the lowland areas of Hungary through the changes in landscapes and the changes in groundwater resources that have the greatest impact on agriculture, using data from more than half of a century. We have quantified that at the mid-territory level (5-10 thousand km2) the groundwater resources show up to 3-5 km3/year changes in both positive and negative directions due to climatic effects. This significantly exceeds the anthropogenic water uses (the total water use of Hungary is about 5 km3 per year), so the effect of climate is the determining factor in the changes of regional water resources. Future changes in water circulation were modelled using the MIKE-SHE model in two micro-regions in Hungary. We have found that already at the level of the small catchments presented in our study, the water shortage increases by hundreds of millions of m3 per year due to the expected increase in temperature (mainly due to the increase in evapotranspiration), which cannot be compensated by current water supply solutions. Model simulations have confirmed previous results showing that groundwater movements play a very important role even in lowland landscapes. Based on our research, we would like to draw the attention of decision-makers and agricultural experts to the fact that current methods (irrigation, regional water transfers) are not sufficient for successful adaptation to climate change. So, it is not the limited precipitation but the inappropriate agricultural practices that cause a real threat in a changing climate. Based on our research, we have made a proposal for the adaptation of agriculture to climate change.

黄土高原油松冠层气孔导度和蒸腾变化特征与模拟

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土高原油松冠层气孔导度和蒸腾变化特征与模拟 DOI: 10.5846/stxb202106041484 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0501603） Characteristics and modeling of canopy stomatal conductance and transpiration of Pinus tabuliformis on the Loess Plateau Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:油松是黄土高原重要的造林树种，模拟其冠层气孔导度和蒸腾对区域水量平衡计算和人工林可持续经营具有重要意义。基于2015-2018年TDP （Thermal dissipation probes）方法所测得液流数据，分析了黄土高原地区油松冠层平均气孔导度（gc）与冠层蒸腾（Tr）的变化特征与影响因素，并采用Penman-Monteith公式和Jarvis型气孔导度模型模拟了其gc和Tr的变化过程，结果表明：（1）该地区油松gc和Tr日内变化均呈现单峰型，日均蒸腾耗水量为（1.25±0.57） mm/d，生长季（4-10月）总蒸腾耗水量均值为195.47 mm。（2）gc的日内变化受太阳辐射（Rad）驱动（偏相关系数为0.65），当Rad高于300 W/m2时，驱动作用减弱；gc的日内变化受水汽压亏缺（VPD）控制（偏相关系数为-0.41），随VPD的增加而降低；gc的日际变化受土壤水分限制（偏相关系数为0.46），当根区相对有效含水率（REW）低于0.45时，限制作用明显。（3）结合Penman-Monteith公式与Jarvis型模型能有效模拟黄土高原油松gc与Tr变化，小时尺度gc与Tr模拟的纳什效率系数（NSE）分别为0.80和0.78，日尺度Tr模拟的NSE为0.76。 Abstract:Pinus tabuliformis is an important afforestation tree species on the Loess Plateau. Accurate estimation of its canopy stomatal conductance and transpiration is of great significance for regional water balance and sustainable forest management. Previous studies have simulated the daily variation of the transpiration of Pinus tabuliformis based on the response of its stomatal conductance to environmental factors, but the influence of soil moisture has not been considered. Soil moisture is one of the most important factors that limit plant transpiration in this region. Considering the response of stomatal conductance to soil moisture is crucial for modeling transpiration. To estimate the transpiration of Pinus tabulaeformis, the trunk sap flow velocity was measured by the thermal dissipation probes (TDP) method from 2015 to 2018. The meteorological factors and soil moisture were also monitored simultaneously. We analyzed the characteristics and controlling factors of the mean canopy stomatal conductance (gc) and transpiration (Tr) of Pinus tabuliformis on the Loess Plateau. Then the Penman-Monteith formula and Jarvis-type stomatal conductance model were used to simulate the process of its gc and Tr. The results showed that:(1) The daily variation of gc and Tr displayed a unimodal curve. The average daily transpiration rate of Pinus tabuliformis was (1.25±0.57) mm/d, and the mean annual total water consumption in the growing season (April to October) was 195.47 mm. (2) Solar radiation (Rad) was the main driving factor of the diurnal variation of gc (the partial correlation coefficient was 0.65), while the driving effect was weakened when the Rad was higher than 300 W/m2. Vapor pressure deficit (VPD) was the main controlling factor of gc diurnal variation (the partial correlation coefficient was -0.41) and gc decreased with the increase of VPD. Soil moisture was the main limiting factor of the daily variation of gc (the partial correlation coefficient was -0.46). When the relative extractable water content (REW) of the root zone was lower than 0.42, gc would decrease rapidly with the decrease of soil moisture. (3) Combining the Penman-Monteith formula and Jarvis-type model could accurately simulate the variation of gc and Tr. The Nash-Sutcliffe efficiency coefficient (NSE) of hourly gc and Tr simulations were 0.80 and 0.78, respectively, while the NSE of daily Tr simulation was 0.76. The parameters of the model obtained in this study were consistent with the basic characteristics of drought tolerance of Pinus tabuliformis, and could provide an important reference for evaluating the canopy stomatal conductance and transpiration variation of the Pinus tabuliformis on the Loess Plateau. 参考文献 相似文献 引证文献

Water resources significance of moisture recycling in the transition zone between Tibetan Plateau and arid region by stable isotope tracing

Moisture recycling, an important component of regional precipitation, is a key indicator of a region's ability to renew its water resources. Quantifying moisture recycling allows for a comprehensive understanding of the spatial and temporal structure of the regional water balance. Therefore, an observation and sampling network for precipitation, soil samples, plant stems, and surface water was established in the Qilian Mountains, a transition zone between the Tibetan Plateau and an arid region. Approximately 2749 samples were collected and analyzed for their isotopic compositions. Based on the Craig–Gordon model and the three-end-member mixing model, the evaporation, transpiration, and advection contributed 8%, 14%, and 78% to precipitation, respectively, and the total contribution to local moisture recycling was equivalent to 71 mm of precipitation. The evaporation fraction tended to decrease from the central Qilian Mountains to the surrounding areas, whereas the transpiration fraction exhibited a decreasing trend from south to north in the south-central Qilian Mountains. If all of the moisture recycling precipitation is produced in the flow, the water production is approximately 13 billion m3, which is approximately 87% of the average total annual runoff from the Qilian Mountains and twice the average total annual runoff of the three major inland river basins in the Hexi corridor. Additionally, altitude, topography, vegetation conditions, and meteorological factors influence local moisture recycling. The results showed that moisture recycling precipitation in cold regions is crucial to ecological stability and water resource supply. This study demonstrates that good ecological conditions enhance moisture recycling, improve the renewal capacity of water resources, and support the stability and sustainable use of regional water resources. Therefore, ecological protection remains an important support for sustainable development in the Qilian Mountains.

Ecological restoration intensifies evapotranspiration in the Kubuqi Desert

Afforestation combats desertification and improves the ecological environment but leads to huge consumption of water resources. Understanding how ecological restoration affects the regional water balance is important for scientific desertification management. Using remote sensing satellite images and meteorological data, we analyzed the impacts of ecological restoration on water resources in the Kubuqi Desert during 1986–2017. Human activities accounted for 60.14% of the desertification reversal: annual average NDVI increased by 94%, the severe desertification area decreased by 30%, and the non-desertification area increased threefold. Vegetation restoration accounted for 70.96% of the evapotranspiration increase of 5.17 mm·yr–1. However, precipitation could not support the increased water demand, which relied on replenishment from groundwater and Yellow River diversion. Therefore, to ensure water security in the Kubuqi, species that use less water should be used in future ecological restoration, and decision-makers should carefully consider the huge water consumption cost of ecological restoration.

Spatial pattern of lake evaporation increases under global warming linked to regional hydroclimate change

Lakes are critical natural resources that are vulnerable to climate change. In a warmer climate, lake evaporation is projected to increase globally, but with substantial variation between regions. Here, based on ensemble projections of climate and lake models and an attribution method, we show that future lake evaporation increase is strongly modulated by regional hydroclimate change. Specifically, a drying hydroclimate will amplify evaporation increase by enlarging surface vapor pressure deficit and reducing cloud shortwave reflection. Future lake evaporation increase is amplified in tropical America, the Mediterranean and Southeast China with drier future hydroclimates, and dampened in high latitudes and the Tibetan Plateau with wetter future hydroclimates. Such spatially coupled changes in lake evaporation and hydroclimate have important implications on regional lake water balance and volume change, which can aggravate water scarcity and flood risks.

The role of snowmelt discharge to runoff of an alpine watershed: Evidence from water stable isotopes

Snow is an important form of water storage which profoundly affects the hydrological processes in alpine watersheds, especially the runoff during snowmelt period. As the strong impact of climate change, the concern about snowmelt water to runoff in alpine watersheds is dramatically growing. However, the studies are mainly focused on arid and semi-arid areas, the research on semi-humid regions sensitive to the climate change need to be strengthened. In this study, for evaluating the contribution of snowmelt water to runoff in snowmelt period, we calculated the stable isotope values (δD, δ18O and d-excess) of different water bodies including river, snow, rain, groundwater, and snowmelt water in the Erdaobaihe River watershed of Changbai Mountains area. The results indicated that the δ18O values of snowmelt water showed an increasing trend with increasing temperature, while the d-excess values of snowmelt water showed a decreasing trend. During the snowmelt period, the snow cover ratio varied from 20.31% to 0.02%. The contribution ratio of snowmelt water to runoff was from 14.4% to 59.8% with average of 42.60% and the total contribution discharge was about 36.56 × 106 m3, which was higher than inland mountainous areas as different elevation and climate. As the stable water source of river, the groundwater contributed 19.2–61.6% with average of 43.88%. The snowmelt water plays an important role in regional water balance. Owing to climate change, the snowfall period in Changbai Mountains was gradually shortening and extreme snowfall events were increasing. The results will provide evidence for further hydrological studies and help to plan future water management strategies in the alpine watershed.

Multiscale gravity measurements to characterize 2020 flood events and their spatio-temporal evolution in Yangtze river of China

In 2020 summer, excessive rainfall pushed rivers and lakes to record high levels over the Yangtze River Basin (YRB), but the five flood peaks were absorbed by the Three Gorges Reservoir (TGR). Mass migration in hydrological processes usually causes the Earth's gravity response, wherefore the 2020 flood events provide a good opportunity to assess the capabilities of gravity measurements in capturing the water mass changes at different scales. In this study, we presents two common gravity measurements (i.e., the satellite mission GRACE-FO and the ground gPhone) used to characterize the evolution of regional floods at a basin- and local- scale, which can be attributed to East Asian rainy season (commonly called “plum rain”) event, i.e., extreme climate-induced effects of the regional water balance, and floodwater absorbed by the reservoir, i.e., the man-made Three Gorges Dam (TGD) intercepting flood peaks. The terrestrial water storage (TWS) estimated by GRACE-FO shows a significant positive anomaly (e.g., ∼370 mm in July and August) in around the TGR. The gPhone measured gravity residual of 10–20 µgal between May and September. The results further suggest that GRACE observation does not have obvious advantages in small-scale TWS monitoring, but gPhone records is difficult to detect the source of the TWS mass change 50 km away. In particular, gPhone recorded the high-frequency gravity disturbance directly related to the high outflow (i.e., >31,000 m3/s) of TGD flood discharge, which is likely used as precursor or co-seismic signal to further study the activity of surface landslide and underground faults induced by the vibration or noise source of the water body. This study shows that the combination of multiscale gravity solutions can potentially detect a wide range of extreme climate events triggered by atmospheric circulation patterns, like El Niño Southern Oscillation and Indian Ocean basin warming accompanied by Sea Surface Temperature (SST) and wind anomalies.

Application of L-band SAR for mapping tundra shrub biomass, leaf area index, and rainfall interception

Rapid shrub expansion has been observed across the Arctic, driving a need for regional-scale estimates of shrub biomass and shrub-mediated ecosystem processes such as rainfall interception. Synthetic-Aperture Radar (SAR) data have been shown sensitive to vegetation canopy characteristics across many ecosystems, thereby potentially providing an accurate and cost-effective tool to quantify shrub canopy cover. This study evaluated the sensitivity of L-band Advanced Land Observing Satellite 2 (ALOS-2) data to the aboveground biomass and Leaf Area Index (LAI) of dwarf birch and alder in the Trail Valley Creek watershed, Northwest Territories, Canada. The σ°VH /σ°VV ratio showed strong sensitivity to both LAI (R2 = 0.72 with respect to in-situ measurements) and wet aboveground biomass (R2 = 0.63) of dwarf birch. Our ALOS-2-derived maps revealed high variability of birch shrub LAI and biomass across spatial scales. The LAI map was fed into the sparse Gash model to estimate shrub rainfall interception, an important but under-studied component of the Arctic water balance. Results suggest that on average across the watershed, 17 ± 3% of incoming rainfall was intercepted by dwarf birch (during summer 2018), highlighting the importance of shrub rainfall interception for the regional water balance. These findings demonstrate the unexploited potential of L-band SAR observations from satellites for quantifying the impact of shrub expansion on Arctic ecosystem processes.

Quantifying the impacts of climate change and vegetation change on decreased runoff in china's yellow river basin

In arid-semiarid regions, understanding the mechanisms by which vegetation change and climate change affect the regional water balance is important for the development of effective measures and for guiding vegetation restoration and adapting to climate change. In this study, we utilize the Budyko equation and dual-source evapotranspiration models to assess the impacts of vegetation change and climate change on the runoff in China's Yellow River Basin (YRB). The aims of the study are as follows: (1) Apply a well-formulated Budyko framework-dual-source evapotranspiration model to explore the eco-hydrological controls of the regional water balance. (2) Precisely assess the contribution of vegetation change, precipitation change, temperature change, wind speed change, the relative humidity change, and radiation change to the decreased runoff. The results indicated that vegetation change was the dominant factor affecting the reduction of runoff in the upper reaches above Lanzhou, Toudaoguai, Longmen, Sanmenxia, and Huayuankou, and the contributions were −80.4%, −58.4%, −52.5%, −46.9%, −39.7%, and −41.6% respectively. In Lanzhou, Taodaoguai, Longmen, and Sanmenxia, the precipitation change was the second affecting factor, and the contributions were −20.8%, −31.6%, −30.0%, and −35.2%, respectively. In Huayuankou and Lijin, the relative humidity change was the second affecting factor, and the contributions were –26.8% and −35.0%, respectively. (3) As the vegetation coverage or the leaf area index (LAI) increased, the runoff decreased linearly.

Identification of conservation priorities in the major basins of Central Asia: Using an integrated GIS-based ordered weighted averaging approach

Ecosystem services (ESs) provided by the major basins of Central Asia are critical to human well-being and have attracted the attention of the international community. The identification of conservation priorities is of great significance for the maintenance and protection of key ESs. In this study, we quantified the spatiotemporal changes of net primary productivity (NPP), soil conservation (SC), water yield (WY) and habitat quality (HQ) in the major basins of Central Asia from 1995 to 2015. In addition, a GIS-based ordered weighted averaging (OWA) multi-criterion valuation method was adopted to identify potential conservation areas under 11 scenarios. Conservation priorities were determined by comparing the conservation efficiency under each scenario. Then, a broad range of indicators were considered to distinguish the driving factors affecting ESs in conservation priorities. The results show that the average conservation efficiency in the Issyk-Kul Basin was the highest, followed by the Am Darya Basin, Ili-Balkhash Basin and Syr Darya Basin. We observed that the conservation efficiency of the four ESs declined continuously in the Ili-Balkhash Basin from 1995 to 2015, while it changed steadily in the other three basins. Correlation analysis indicated that natural factors (e.g., precipitation and topography) were the main driving factors of WY, SR and NPP in conservation priorities, while HQ was more affected by socio-economic factors (e.g., population density and both cropland and urban percentages). The identification of conservation priorities and their driving factors plays an important role in ensuring the ecological security of the lower reaches, regulating the regional water balance and stabilizing the climate pattern.