Canopy Water Storage Research Articles

Aboveground biomass determines canopy rainfall interception loss in Semiarid Grassland Communities

AbstractCanopy rainfall interception is one key hydrological process, affecting rainwater redistribution and effectiveness in semiarid regions. Canopy rainfall interception loss is jointly influenced by meteorology, vegetation and topography. The canopy water storage capacity (S), rainfall interception depth (Im) and ratio (I%) and vegetation characteristics, together with topographic factors of three grassland communities (dominated by Bothriochloa ischaemum, Lespedeza davurica and Artemisia gmelinii, respectively) were investigated on the Loess Plateau of China during the main growing season (June to September). Results showed that Im ranged from 0.55 to 0.89 mm and I% ranged from 6.14% to 12.1%, with the maximum values occurring in August for three communities, and A. gmelinii community had the largest Im (0.89 mm) and I% (12.1%). The Im and I% were positively correlated with aboveground biomass (AGB), coverage (Cov), leaf area index (LAI), community‐weighted mean height (CWMH) and altitude (Alt), but negatively correlated with slope degree and rainfall intensity (RI). Hierarchical partitioning analysis (HPA) showed that AGB had the highest contribution for Im (20.3%), while Alt had the highest contribution for I% (18.2%). The regression models based on forward selection could effectively predict the values of Im (R2 = 0.802, RMSE = 0.049) and I% (R2 = 0.546, RMSE = 1.434). Topographic factors (altitude, slope degree and aspect) indirectly influenced both Im and I% by modulating vegetation characteristics (AGB, Cov, etc.). All these indicated that aboveground biomass mainly determines grassland community rainfall interception loss in the semiarid Loess Plateau.

Evaluating dynamics of land water storage and its response to climate variation in the Deccan Plateau, India

Inter-state river water disputes are frequent over the rain shadow (RS) region of the Western Ghats (WG), where the annual rainfall is much lower (75.2 cm) than that of overall India (118 cm). This study investigated the TWS (Terrestrial Water Storage) dynamics of the entire Deccan plateau (DP) and RS regions, located at the leeward side of the WG mountain range, with the help of Gravity Recovery and Climate Experiment (GRACE) based TWS anomalies (TWSA) data. Here, the latest TRMM (Tropical Rainfall Measuring Mission) rainfall product was evaluated at different time scales against gauge-based measurements to check its applicability as an alternative to gauge-based observed data. Trends in climate variables and TWSA were estimated to understand their variations during 2003–2016 in both regions. The response of GRACE-based TWSA and its constituent components to rainfall was determined using time-lagged correlation analysis. The contribution of constituent variables to TWSA was estimated using the component contribution ratio (CCR) method. It was observed that the TRMM-3B43 data captured the rainfall pattern over the entire DP with great accuracy. Results showed that the increasing trend of TWS in 2003–2009 had reversed in 2010–2016 due to the reduction of climate moistening in both regions. The warming trend of climate is more than twice in the RS region than that found in the DP, leading to a higher decreasing rate of TWS in this region than in DP. For both DP and RS regions, the time lags of groundwater storage anomalies (GWSA), total runoff anomalies (RA), canopy water storage anomalies (CWSA), and soil moisture storage anomalies (SMSA) to rainfall can be arranged as CWSA ≤ RA ≤ SMSA ≤ GWSA. SMSA and GWSA are the main contributors to the TWSA in both areas. However, SWSA also played a vital role in TWS variability, particularly in the RS region.

Estimating rainfall interception of xerophytic deciduous shrubs by static- and variable-parameter Gash models with stem- and leaf-dominated canopy water storage

The precise modeling of rainfall interception is important to understand the water balance of forest ecosystems, particularly in water-stressed restoration regions. However, xerophytic deciduous shrubs are currently underrepresented in rainfall interception models due to the significant variations in their canopy structures. Therefore, we estimated the rainfall interceptions of four representative deciduous shrubs (Spiraea pubescens, Potentilla fruticose, Hippophae rhamnoides, and Caragana korshinskii) in the semiarid region of northern China using the revised Gash model (RG model) with static parameters and a modified Gash model (MG model) with variable parameters. The results indicate that the MG model outperformed the RG model in studies of S. pubescens and P. fruticose, with regard to the modeling error (6.6%–7.9%), Nash–Sutcliffe model efficiency (0.68–0.86), and the root-mean-square error (0.17–0.71). However, the RG model was better than the MG model for H. rhamnoides and C. korshinskii, with regard to the modeling error (3.6%–6.3%), Nash–Sutcliffe model efficiency (0.82–0.94), and the root-mean-square error (0.17–0.66). The MG model was highly sensitive to changes in the leaf area index, canopy cover, mean evaporation rate, canopy storage capacity, and leaf storage capacity for S. pubescens and P. fruticose. Nevertheless, the RG model demonstrated high sensitivity to changes in the canopy storage capacity and stem storage capacity for H. rhamnoides and C. korshinskii. These indicated that canopy storage capacity has a significant effect on the rainfall interception capabilities of different shrub species, as indicated by both the RG and MG models. This critical indicator was determined by the water storage of stems for H. rhamnoides and C. korshinskii (ranged contribution of 59.5%–81.6%), whereas the water storage of leaves for S. pubescens and P. fruticose (with contributions of 51.3%–80.7%). Therefore, the optimized RG and MG models are recommended for estimating the rainfall interception of xerophytic shrubs with stem-dominated water storage and leaf-dominated water storage, respectively. This study categorizes the applicability of rainfall interception models in terms of important plant traits to precisely assess the water balance of xerophytic deciduous shrub ecosystems. In future studies, leaf configuration and hydrophobicity are highly recommended to be quantified for further improving rainfall interception models.

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.

The detected effects of driptips and leaf wettability on the kinetic energy of throughfall in rubber‐based agroforestry in Xishuangbanna

AbstractDriptips play important roles in controlling soil erosion and in the water cycle. The driptips size distribution and the morphology of water droplets on the leaves among rubber (Hevea brasiliensis) and intercropping species (Camellia sinensis, Citrus reticulata, Flemingia macrophylla and Theobroma cacao) were measured. Driptip‐producing experiments were conducted indoors on stabilized leaves of five species with artificially mist spray. In all five foliage species, the diameter of the driptips from rubber leaves was the lowest. Furthermore, the relationship between driptips size and the mean leaf width at 3 mm from the rubber leaf tip was significantly positively correlated. Leaf wettability as measured by water droplets height linearly increase with the total volume of water which dropped on the leaves of all five species. The contact angle of the water droplets and the total volume of the droplet were significantly negatively correlated. Based on physical theory, the kinetic energy of the driptips was calculated by estimating the diameters of the driptip from all five species. The results indicated that it was important to consider the kinetic energy of driptips in selection of intercropping species when constructing rubber‐based agroforestry plantations. Understanding the relationship between driptips size and the development of leaf tips (leaf width at 3 mm from the leaf tip) will require more experiments with different leaf inclinations, and the results also confirmed that using the contact angle of water droplets to assess leaf wettability. This study can help to predict canopy water processes, such as canopy water storage and drainage.

The contribution of understory and Compositae species to canopy storage capacity of semiarid grassland communities on the Loess Plateau

AbstractCanopy rainfall interception reduces the effectiveness of limited rainfall resources in arid and semiarid regions. To clarify the effects of species composition and community vertical structure on canopy storage capacity, the artificial wetting and simulated rainfall methods were used to determine the species (C) and community (Cmax) water storage, respectively, in three typical grassland communities on the semiarid Loess Plateau. Results indicated that water storage capacity of 31 grassland species ranged from 0.47 to 3.73 g g−1, with an average of 1.60 g g−1, and leaf storage capacity was significantly higher than the stem. Plant storage capacity was correlated with leaf traits (including leaf fresh weight, length and area). Canopy storage capacity of three grassland communities (Bothriochloa ischaemum, Artemisia gmelinii and Lespedeza davurica) ranged from 0.77 to 1.09 mm and were positively correlated with community leaf area index (LAI), coverage and leaf dry biomass. Leaf and stem water storage accounted for 57.6% and 42.4% of the total community, respectively. The water storage of Compositae, Gramineae, Leguminosae and other species accounted for 35.5%, 27.0%, 23.4% and 14.1%, respectively. The plants in the community with heights of >40, 20–40 and 0–20 cm contributed 5.8%, 30.3% and 63.9% of the water storage, respectively. The field observed canopy storage capacity was significantly higher than the estimated value through scaling up the individual storage data to the community, revealing complex community structure and species composition may increase actual rainfall interception. These results highlighted the species at 0–20 cm height was the key component affecting canopy water storage, and Compositae species may intercept more rainfall within the community, which imply that reducing the understory or Compositae species composition of grassland community would be helpful for increasing limited rainfall partitioning to soil in the drought area.

Inter- and intra-event rainfall partitioning dynamics of two typical xerophytic shrubs in the Loess Plateau of China

Abstract. Rainfall is known as the main water replenishment in dryland ecosystems, and rainfall partitioning by vegetation reshapes the spatial and temporal distribution patterns of rainwater entry into the soil. The dynamics of rainfall partitioning have been extensively studied at the inter-event scale, yet very few studies have explored its finer intra-event dynamics and the relating driving factors for shrubs. Here, we conducted a concurrent in-depth investigation of all rainfall partitioning components at inter- and intra-event scales for two typical xerophytic shrubs (Caragana korshinskii and Salix psammophila) in the Liudaogou catchment of the Loess Plateau, China. The event throughfall (TF), stemflow (SF), and interception loss (IC), and their temporal variations within the rainfall event, as well as the meteorological factors and vegetation characteristics, were systematically measured during the 2014–2015 rainy seasons. Our results showed that C. korshinskii had significantly higher SF percentage (9.2 %) and lower IC percentage (21.4 %) compared to S. psammophila (3.8 % and 29.5 %, respectively), but their TF percentages were not significantly different (69.4 % vs. 66.7 %). At the intra-event scale, TF and SF of S. psammophila were initiated (0.1 vs. 0.3 h and 0.7 vs. 0.8 h) and peaked (1.8 vs. 2.0 h and 2.1 vs. 2.2 h) more quickly, and TF of S. psammophila lasted longer (5.2 vs. 4.8 h) and delivered more intensely (4.3 vs. 3.8 mm h−1), whereas SF of C. korshinskii lasted longer (4.6 vs. 4.1 h) and delivered more intensely (753.8 vs. 471.2 mm h−1). For both shrubs, rainfall amount was the most significant factor influencing inter-event rainfall partitioning, and rainfall intensity and duration controlled the intra-event TF and SF variables. The C. korshinskii with larger branch angle, more small branches, and smaller canopy area, has an advantage over S. psammophila to produce SF more efficiently. The S. psammophila has lower canopy water storage capacity to generate and peak TF and SF earlier, and it has larger aboveground biomass and total canopy water storage of individual plants to produce higher IC compared to C. korshinskii. These findings contribute to the fine characterization of shrub-dominated ecohydrological processes, and improve the accuracy of water balance estimation in dryland ecosystems.

Comparison of Different Methods to Estimate Canopy Water Storage Capacity of Two Shrubs in the Semi-Arid Loess Plateau of China

The canopy water storage capacity of vegetation has great significance for the hydrological cycle. We used the Pereira regression analysis method, scale-up method, and simulated rainfall method to determine canopy water storage capacity from 2014 to 2018. The Pereira regression analysis was affected mainly by the seasonal variation in the leaf area index and the observation method of throughfall. The canopy water storage capacity was 0.68 mm and 0.72 mm for C. korshinskii and H. rhamnoides, respectively. The canopy water storage capacity of C. korshinskii and H. rhamnoides was 0.73 mm and 0.76 mm, respectively, using the scale-up method. The scale-up method showed that water storage capacity per area of the canopy components was in the order of branches (0.31 mm) > leaves (0.27 mm) > trunks (0.15 mm) for C. korshinskii, and trunks (0.33 mm) > branches (0.29 mm) > leaves (0.14 mm) for H. rhamnoides. We used eight simulated rainfall intensities to determine the canopy water storage capacity for C. korshinskii and H. rhamnoides, which was 0.63 mm and 0.59 mm, respectively.

Monitoring Tree Sway as an Indicator of Interception Dynamics Before, During, and Following a Storm

AbstractUnderstanding the role of trees in attenuating the timing and magnitude of effective precipitation reaching the land surface requires improved monitoring of interception dynamics. We developed a new field monitoring approach to leverage continuous monitoring of tree sway motion in quantifying continuous, dynamic time series of canopy water storage during storms. Using this approach, we additionally observed a hysteretic interception response in tree canopies, which indicates that interpreting interception processes through tree sway signals requires the consideration of changing water (i.e., mass) distribution during and following storms. These findings suggest that continuously monitoring tree sway motions offers a new technique to quantify interception processes. This advancement in whole tree interception may help improve our understanding of how interception affects ecosystem water availability/productivity and runoff dynamics that are important for both natural ecosystems and stormwater management in cities.

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.

Stand-Level Variation Drives Canopy Water Storage by Non-vascular Epiphytes Across a Temperate-Boreal Ecotone

Epiphytes, including bryophytes and lichens, can significantly change the water interception and storage capacities of forest canopies. However, despite some understanding of this role, empirical evaluations of canopy and bole community water storage capacity by epiphytes are still quite limited. Epiphyte communities are shaped by both microclimate and host plant identity, and so the canopy and bole community storage capacity might also be expected to vary across similar spatial scales. We estimated canopy and bole community cover and biomass of bryophytes and lichens from ground-based surveys across a temperate-boreal ecotone in continental North America (Minnesota). Multiple forest types were studied at each site, to separate stand level and latitudinal effects. Biomass was converted into potential canopy and bole community storage on the basis of water-holding capacity measurements of dominant taxa. Bole biomass and potential water storage was a much larger contributor than outer canopy. Biomass and water storage capacity varied greatly, ranging from 9 to >900kg ha–1 and 0.003 to 0.38 mm, respectively. These values are lower than most reported results for temperate forests, which have emphasized coastal and old-growth forests. Variation was greatest within sites and appeared to reflect the strong effects of host tree identity on epiphyte communities, with conifer-dominated plots hosting more lichen-dominated epiphyte communities with lower potential water storage capacity. These results point to the challenges of estimating and incorporating epiphyte contributions to canopy hydrology from stand metrics. Further work is also needed to improve estimates of canopy epiphytes, including crustose lichens.

Can a physically-based land surface model accurately represent evapotranspiration partitioning? A case study in a humid boreal forest

One of the roles of Land Surface Models (LSMs) is to partition evapotranspiration (E) into overstory transpiration (ET), understory evapotranspiration (EG), and wet canopy evaporation (EC). Unfortunately, only a handful of studies have evaluated the performance of LSMs with E partitioning. Unlike dry canopies which are dominated by transpiration, wet canopies lead to the evaporation of intercepted water. In this respect, there is no better testing site for LSMs than the humid boreal forest, which is characterized by frequent precipitation and sustained evapotranspiration. This study assesses the performance of the Canadian Land Surface Scheme (CLASS) in simulating evapotranspiration and its components by applying detailed observations of water pathways and residence times in a forest canopy using a variety of methods (eddy covariance; sap flow, throughfall and stemflow measurements; and the stem compression approach). The study site was located in Montmorency Forest in Québec, Canada, a balsam fir boreal forest with ≈1600 mm of annual precipitation. The field campaign was conducted during the summers of 2017 and 2018. To improve the accuracy of the simulations, we adjusted the definition of maximum canopy water storage, S=c×LAI, by using c=0.49 mm instead of the default value of 0.20 mm. This simple modification improved the performance of CLASS when simulating components of evapotranspiration, indicated by the increase in the modified Kling-Gupta efficiency (KGE′) with rises between 0.01 and 0.23. Overall, CLASS performed well in simulating evapotranspiration and overstory transpiration in dry canopy conditions at half-hourly time steps with KGE′ values between 0.67 and 0.81. The contribution of simulated ET,EG, and EC to total E during the two sampling periods were 46%,24%, and 30%, respectively, which were comparable with the field observations (35%,22%, and 25%, respectively). In conclusion, CLASS was able to simulate E partitioning in dry and wet canopy conditions reasonably well at both seasonal and half-hourly time scales.

Groundwater Depletion Signals in the Beqaa Plain, Lebanon: Evidence from GRACE and Sentinel-1 Data

Regions with high productivity of agriculture, such as the Beqaa Plain, Lebanon, often rely on groundwater supplies for irrigation demand. Recent reports have indicated that groundwater consumption in this region has been unsustainable, and quantifying rates of groundwater depletion has remained a challenge. Here, we utilize 15 years of data (June 2002–April 2017) from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to show Total Water Storage (TWS) changes in Lebanon’s Beqaa Plain. We then obtain complimentary information on various hydrologic cycle variables, such as soil moisture storage, snow water equivalent, and canopy water storage from the Global Land Data Assimilation System (GLDAS) model, and surface water data from the largest body of water in this region, the Qaraaoun Reservoir, to disentangle the TWS signal and calculate groundwater storage changes. After combining the information from the remaining hydrologic cycle variables, we determine that the majority of the losses in TWS are due to groundwater depletion in the Beqaa Plain. Results show that the rate of groundwater storage change in the West Beqaa is nearly +0.08 cm/year, in the Rashaya District is −0.01 cm/year, and in the Zahle District the level of depletion is roughly −1.10 cm/year. Results are confirmed using Sentinel-1 interferometric synthetic aperture radar (InSAR) data, which provide high-precision measurements of land subsidence changes caused by intense groundwater usage. Furthermore, data from local monitoring wells are utilized to further showcase the significant drop in groundwater level that is occurring through much of the region. For monitoring groundwater storage changes, our recommendation is to combine various data sources, and in areas where groundwater measurements are lacking, we especially recommend the use of data from remote sensing.

Variability of Leaf Wetting and Water Storage Capacity of Branches of 12 Deciduous Tree Species

Leaf surface wettability and factors which determine it are key in determining the water storage capacity of tree crowns and thus the interception of entire stands. Leaf wettability, expressed as the droplet inclination angle, and the surface free energy largely depend not only on the chemical composition of the leaves but also on their texture. The study concerns 12 species of trees common in Central Europe. The content of epicuticular waxes was determined in the leaves, and values ranging from 9.145 [µg/cm2] for horse chestnut (Aesculus hippocastanum L.) to 71.759 [µg/cm2] for birch (Betula pendula Roth.) were obtained. Each additional µg/cm2 increases the canopy water storage capacity by 0.067 g g−1. For all species, the inclination angles of water, diiodomethane and glycerin droplets to the leaf surface were measured and the surface free energy was calculated. It is shown that it is the wax content and the species that constitute independent predictors of water storage capacity. These factors explain the 95.56% effect on the value of canopy water storage capacity. The remaining 4.44% indicate non-species-related individual features or the ability to mitigate pollutants as well as possible environmental factors. Wax analyzed separately from other factors causes a slight increase (by 0.067 g/g) of S. Nevertheless, the influence of the surface condition as a result of species-related variability is decisive for the value of the canopy water storage capacity.

The influence of assimilating leaf area index in a land surface model on global water fluxes and storages

Abstract. Vegetation plays a fundamental role not only in the energy and carbon cycles but also in the global water balance by controlling surface evapotranspiration (ET). Thus, accurately estimating vegetation-related variables has the potential to improve our understanding and estimation of the dynamic interactions between the water, energy, and carbon cycles. This study aims to assess the extent to which a land surface model (LSM) can be optimized through the assimilation of leaf area index (LAI) observations at the global scale. Two observing system simulation experiments (OSSEs) are performed to evaluate the efficiency of assimilating LAI into an LSM through an ensemble Kalman filter (EnKF) to estimate LAI, ET, canopy-interception evaporation (CIE), canopy water storage (CWS), surface soil moisture (SSM), and terrestrial water storage (TWS). Results show that the LAI data assimilation framework not only effectively reduces errors in LAI model simulations but also improves all the modeled water flux and storage variables considered in this study (ET, CIE, CWS, SSM, and TWS), even when the forcing precipitation is strongly positively biased (extremely wet conditions). However, it tends to worsen some of the modeled water-related variables (SSM and TWS) when the forcing precipitation is affected by a dry bias. This is attributed to the fact that the amount of water in the LSM is conservative, and the LAI assimilation introduces more vegetation, which requires more water than what is available within the soil.

Integrated study of GRACE data derived interannual groundwater storage variability over water stressed Indian regions

Groundwater serves more than 80% of agriculture and 60% of drinking water in India thus making it a demandable resource in the study area. In this study the groundwater storage change was determined by using RL05 land data product (January, 2003 to December, 2016) which was accessed from the Gravity Recovery and Climate Experiment (GRACE) satellite. Total soil moisture (up to 2m depth), canopy water storage and snow water equivalent derived from Global Land Data Assimilation System (GLDAS) NOAH was subtracted from terrestrial water storage (TWS) for extracting the groundwater component, revealing maximum groundwater storage change by −7.52 cm/year in Delhi, northern Uttar Pradesh and some parts of Haryana. In water stressed regions of India (January 2003 to December 2016) the groundwater depletion rate in the cities of Delhi, Meerut, Dehradun and Chandigarh are −3.682 ± 0.8 cm/year, −3.62 ± 0.7 cm/year, −3.1 ± 0.87 cm/year, −2.73 ± 0.6 cm/year respectively. The groundwater storage change (GWSC) depletion rate observed in Delhi, Meerut, Dehradun, Chandigarh in January 2003 to May 2010 are −3.43 ± 1.37, −3.41 ± 1.22, −3.72 ± 1.52, −3.43 ± 1.05 cm/year respectively and in August 2010 to December 2016 depletion rate is −5.53 ± 1.57, −7.12 ± 1.40, −4.98 ± 1.74,-3.92 ± 1.20 cm/year respectively. The data obtained by GRACE/GLDAS-derived total GWS (cm) and Global Positioning System (GPS)-derived vertical deformation of International GNSS services (IGS) station, at Indian Institute of Science (IISc) Bangalore (2014–2016) is correlated by 0.71. Analysis conducted in metro cities (Delhi, Chennai, Bengaluru, Kolkata and Mumbai) shows with time succession groundwater storage has suffered a major depletion in spite of quantified rainfall in these places. The GRACE-derived GWSC values agrees reasonably with in-situ well observations by Pearson's coefficient; 0.89, 0.88, 0.87 and 0.74 for Delhi, Haryana, Punjab and Uttar Pradesh thereby justifying remote sensing approach and further substantiate our research study that regional GWS mapping can be achieved by the GRACE mission rapidly and accurately.

Partitioning of rainfall in a seasonal dry tropical forest

Rainfall redistribution by forest cover has potential hydrological impacts in semi-arid regions due to continuous human intervention. Studying the process of interception loss by Caatinga vegetation and its changes due to deforestation is extremely important for local hydrology. However, such information is scarce in the literature. This study examined the partitioning of rainfall into throughfall (TF), stemflow (SF) and interception loss (I) in the Caatinga vegetation (CAA) and evaluated the influence of rainfall characteristics on this partitioning. The components of rainfall partitioning were measured from 2016 to 2017 to determine the TF and SF respectively, and their relationships with rainfall characteristics were evaluated based on linear regression models. For the Caatinga vegetation, TF and SF represent 89.2% and 0.5% of the gross rainfall, while interception loss was 10.3%, an expressive value that should be included in regional water balance models. The rainfall characteristics were able to explain the variations in water partitioning, showing that TF and SF increase for events of higher intensity and volume, whereas interception loss is mainly associated with events of longer duration. For the Caatinga, stemflow and throughfall usually occur for events of greater than 1.65 mm and 0.98 mm, while values for canopy water storage ranged from 0.88 mm to 1.16 mm. It is concluded that for semi-arid environments, these values are significant and cannot be ignored when managing local water resources.

Spatial and Temporal Variations of Terrestrial Water Storage in Upper Indus Basin Using GRACE and Altimetry Data

Gravity Recovery and Climate Experiment (GRACE) and satellite altimetry are suitable for the precise measurement of terrestrial water storage (TWS) and lake water level variations from space. In this study, two GRACE solutions, namely, spherical harmonics (SH) and mascon (MSC), are utilized with the Global Land Data Assimilation System (GLDAS) model to estimate the spatial and temporal variations of TWS in the Upper Indus Basin (UIB) for the study period of January 2003 to December 2016. The TWS estimated by SH, MSC, and the GLDAS model are consistent and generally show negative trends of -4.47 ± 0.38 mm/year, -4.81 ± 0.49 mm/year, and -3.77 ± 0.46 mm/year, respectively. Moreover, we use the GLDAS model data to understand the roles of variations in land surface state variables (snow water equivalent (SWE), soil moisture, and canopy water storage) in enhancing or dissipating the TWS in the region. Results indicate that SWE, which has a significant contribution to GRACE TWS variability, is an important parameter. Spearman's rank correlations are calculated to demonstrate the relationship of the GLDAS land surface state variables and the GRACE signals. A highly positive correlation between SWE with TWS is estimated by SH and MSC as 0.691 and 0.649, respectively, indicating that the TWS signal is mainly reliant on snow water in the study region. The ground water storages estimated by SH and MSC solutions are nearly stable with slight increasing trends of 0.63 ± 0.48 mm/year and 0.29 ± 0.51 mm/year, respectively. We also take advantage of the potential of satellite altimetry in measuring lake water level variations, and our result indicates that Cryosat-2 SARin mode altimetry data can be used in estimating small water bodies accurately in the high mountainous region of the UIB. Moreover, the climate indices data of El-Niño Southern Oscillation and Pacific Decadal Oscillation are analyzed to determine the influence of pacific climatic variability on TWS.

Differences in Response of Terrestrial Water Storage Components to Precipitation over 168 Global River Basins

AbstractA time lag exists between precipitation P falling and being converted into terrestrial water. The responses of terrestrial water storage (TWS) and its individual components to P over the global scale, which are vital for understanding the interactions and mechanisms between climatic variables and hydrological components, are not well constrained. In this study, relying on land surface models, we isolate five component storage anomalies from TWS anomalies (TWSA) derived from the Gravity Recovery and Climate Experiment mission (GRACE): canopy water storage anomalies (CWSA), surface water storage anomalies (SWSA), snow water equivalent anomalies (SWEA), soil moisture storage anomalies (SMSA), and groundwater storage anomalies (GWSA). The responses of TWSA and of the individual components of TWSA to P are then evaluated over 168 global basins. The lag between TWSA and P is quantified by calculating the correlation coefficients between GRACE-based TWSA and P for different time lags, then identifying the lag (measured in months) corresponding to the maximum correlation coefficient. A multivariate regression model is used to explore the relationship between climatic and basin characteristics and the lag between TWSA and P. Results show that the spatial distribution of TWSA trend presents a similar global pattern to that of P for the period January 2004–December 2013. TWSA is positively related to P over basins but with lags of variable duration. The lags are shorter in the low- and midlatitude basins (1–2 months) than those in the high-latitude basins (6–9 months). The spatial patterns of the maximum correlations and the corresponding lags between individual components of the TWSA and P are consistent with those of the GRACE-based analysis, except for SWEA (3–8 months) and CWSA (0 months). The lags between GWSA, SMSA, and SWSA to P can be arranged as GWSA > SMSA ≥ SWSA. Regression analysis results show that the lags between TWSA and P are related to the mean temperature, mean precipitation, mean latitude, mean longitude, mean elevation, and mean slope.

RETRACTED: Study on the throughfall, stemflow, and interception of two shrubs in the semiarid Loess region of China

Abstract The Loess Plateau, China, has been subject to 40 years of re-vegetation predominantly with the xerophytic shrubs Caragana korshinskii and Hippophae rhamnoides. Throughfall, stemflow, canopy interception, and water storage capacity experiments for the two shrubs were conducted from May to September during the period 2009–2013. The results showed that the throughfall percentages averaged 62.4% and 70.1% of gross rainfall for H. rhamnoides and C. korshinskii, respectively, while stemflow accounted for 2.4% and 6.7% of the gross rainfall for the two shrubs. The rainfall threshold for stemflow generation was 2.46 and 1.06 mm for H. rhamnoides and C. korshinskii, respectively. The wetting front depths for the two shrubs in the area around the stems were deeper than away from the shrubs. The averaged percentages of interception loss in H. rhamnoides and C. korshinskii were 35.2% and 23.2%. Additionally, H. rhamnoides had greater water storage capacity per leaf area for each simulated rainfall intensity (mean, 0.59 mm; range, 0.28–0.88 mm) than C. korshinskii (mean, 0.44 mm; range, 0.26–0.52 mm). Canopy water storage varied temporally with the eight simulated rainfall intensities. For all the tested rainfall intensities, H. rhamnoides could store more water per dry biomass (mean, 0.72 g−1; range, 0.39–1.06 g−1) than C. korshinskii (mean, 0.49 g−1; range, 0.31–0.69 g−1). The present study can inform re-vegetation projects, water budget analyses, and modeling efforts aimed at understanding rainfall water movement within shrub communities in the semiarid Chinese Loess Plateau, China.