scholarly journals Improved Mekong Basin Runoff Estimate and Its Error Characteristics Using Pure Remotely Sensed Data Products

2021 ◽  
Vol 13 (5) ◽  
pp. 996
Author(s):  
Hok Sum Fok ◽  
Yutong Chen ◽  
Lei Wang ◽  
Robert Tenzer ◽  
Qing He
Keyword(s):  
Water Balance ◽  
Balance Equation ◽  
Remotely Sensed ◽  
Water Balance Equation ◽  
Water Balance Component ◽  
Mekong Basin ◽  
Data Products ◽  
Terrestrial Water ◽  
Published Result

Basin runoff is a quantity of river discharge per unit basin area monitored close to an estuary mouth, essential for providing information on the flooding and drought conditions of an entire river basin. Owing to a decreasing number of in situ monitoring stations since the late 1970s, basin runoff estimates using remote sensing have been advocated. Previous runoff estimates of the entire Mekong Basin calculated from the water balance equation were achieved through the hybrid use of remotely sensed and model-predicted data products. Nonetheless, these basin runoff estimates revealed a weak consistency with the in situ ones. To address this issue, we provide a newly improved estimate of the monthly Mekong Basin runoff by using the terrestrial water balance equation, purely based on remotely sensed water balance component data products. The remotely sensed water balance component data products used in this study included the satellite precipitation from the Tropical Rainfall Measuring Mission (TRMM), the satellite evapotranspiration from the Moderate Resolution Imaging Spectroradiometer (MODIS), and the inferred terrestrial water storage from the Gravity Recovery and Climate Experiment (GRACE). A comparison of our new estimate and previously published result against the in situ runoff indicated a marked improvement in terms of the Pearson’s correlation coefficient (PCC), reaching 0.836 (the new estimate) instead of 0.621 (the previously published result). When a three-month moving-average process was applied to each data product, our new estimate further reached a PCC of 0.932, along with the consistent improvement revealed from other evaluation metrics. Conducting an error analysis of the estimated mean monthly runoff for the entire data timespan, we found that the usage of different evapotranspiration data products had a substantial influence on the estimated runoff. This indicates that the choice of evapotranspiration data product is critical in the remotely sensed runoff estimation.

scholarly journals Estimation of Terrestrial Water Storage Changes at Small Basin Scales Based on Multi-Source Data

2021 ◽  
Vol 13 (16) ◽  
pp. 3304
Author(s):  
Qin Li ◽  
Xiuguo Liu ◽  
Yulong Zhong ◽  
Mengmeng Wang ◽  
Shuang Zhu
Keyword(s):  
Water Balance ◽  
Balance Equation ◽  
Water Storage ◽  
Terrestrial Water Storage ◽  
Runoff Simulation ◽  
Satellite Mission ◽  
Water Balance Equation ◽  
Source Data ◽  
Terrestrial Water ◽  
Small Basin

Terrestrial water storage changes (TWSCs) retrieved from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have been extensively evaluated in previous studies over large basin scales. However, monitoring the TWSC at small basin scales is still poorly understood. This study presented a new method for calculating TWSCs at the small basin scales based on the water balance equation, using hydrometeorological and multi-source data. First, the basin was divided into several sub-basins through the slope runoff simulation algorithm. Secondly, we simulated the evapotranspiration (ET) and outbound runoff of each sub-basin using the PML_V2 and SWAT. Lastly, through the water balance equation, the TWSC of each sub-basin was obtained. Based on the estimated results, we analyzed the temporal and spatial variations in precipitation, ET, outbound runoff, and TWSC in the Ganjiang River Basin (GRB) from 2002 to 2018. The results showed that by comparing with GRACE products, in situ groundwater levels data, and soil moisture storage, the TWSC calculated by this study is in good agreement with these three data. During the study period, the spatial and temporal variations in precipitation and runoff in the GRB were similar, with a minimum in 2011 and maximum in 2016. The annual ET changed gently, while the TWSC fluctuated greatly. The findings of this study could provide some new information for improving the estimate of the TWSC at small basin scales.

scholarly journals How well are we able to close the water budget at the global scale?

2022 ◽  
Vol 26 (1) ◽  
pp. 35-54
Author(s):  
Fanny Lehmann ◽  
Bramha Dutt Vishwakarma ◽  
Jonathan Bamber
Keyword(s):  
Water Balance ◽  
Balance Equation ◽  
Land Surface ◽  
Water Budget ◽  
Global Scale ◽  
Surface Model ◽  
Catchment Scale ◽  
Satellite Mission ◽  
Water Balance Equation ◽  
Data Products

Abstract. The water budget equation describes the exchange of water between the land, ocean, and atmosphere. Being able to adequately close the water budget gives confidence in our ability to model and/or observe the spatio-temporal variations in the water cycle and its components. Due to advances in observation techniques, satellite sensors, and modelling, a number of data products are available that represent the components of water budget in both space and time. Despite these advances, closure of the water budget at the global scale has been elusive. In this study, we attempt to close the global water budget using precipitation, evapotranspiration, and runoff data at the catchment scale. The large number of recent state-of-the-art datasets provides a new evaluation of well-used datasets. These estimates are compared to terrestrial water storage (TWS) changes as measured by the Gravity Recovery And Climate Experiment (GRACE) satellite mission. We investigated 189 river basins covering more than 90 % of the continental land area. TWS changes derived from the water balance equation were compared against GRACE data using two metrics: the Nash–Sutcliffe efficiency (NSE) and the cyclostationary NSE. These metrics were used to assess the performance of more than 1600 combinations of the various datasets considered. We found a positive NSE and cyclostationary NSE in 99 % and 62 % of the basins examined respectively. This means that TWS changes reconstructed from the water balance equation were more accurate than the long-term (NSE) and monthly (cyclostationary NSE) mean of GRACE time series in the corresponding basins. By analysing different combinations of the datasets that make up the water balance, we identified data products that performed well in certain regions based on, for example, climatic zone. We identified that some of the good results were obtained due to the cancellation of errors in poor estimates of water budget components. Therefore, we used coefficients of variation to determine the relative quality of a data product, which helped us to identify bad combinations giving us good results. In general, water budget components from ERA5-Land and the Catchment Land Surface Model (CLSM) performed better than other products for most climatic zones. Conversely, the latest version of CLSM, v2.2, performed poorly for evapotranspiration in snow-dominated catchments compared, for example, with its predecessor and other datasets available. Thus, the nature of the catchment dynamics and balance between components affects the optimum combination of datasets. For regional studies, the combination of datasets that provides the most realistic TWS for a basin will depend on its climatic conditions and factors that cannot be determined a priori. We believe that the results of this study provide a road map for studying the water budget at catchment scale.

scholarly journals Evaluation of Evapotranspiration for Exorheic Catchments of China during the GRACE Era: From a Water Balance Perspective

2020 ◽  
Vol 12 (3) ◽  
pp. 511 ◽  
Author(s):  
Yulong Zhong ◽  
Min Zhong ◽  
Yuna Mao ◽  
Bing Ji
Keyword(s):  
Water Balance ◽  
Balance Equation ◽  
Land Surface ◽  
Regional Scale ◽  
Water Balance Equation ◽  
Direct Measurements ◽  
Terrestrial Water ◽  
Gravity Recovery ◽  
The Impact ◽  
Mean Square Errors

Evapotranspiration (ET) is usually difficult to estimate at the regional scale due to scarce direct measurements. This study uses the water balance equation to calculate the regional ET with observations of precipitation, runoff, and terrestrial water storage changes (TWSC) in nine exorheic catchments of China. We compared the regional ET estimates from a water balance perspective with and without considering TWSC (ETWB: ET estimates with considering TWSC, and ETPQ: ET estimates from precipitation minus runoff without considering TWSC). Results show that the regional annual ET ranges from 417.7 mm/yr to 831.5 mm/yr in the nine exorheic catchments based on the water balance equation. The impact of ignoring TWSC on calculating ET is notable, as the root mean square errors (RMSEs) of annual ET between ETWB and ETPQ range from 12.0–105.8 mm/yr (2.6–12.7% in corresponding annual ET) among the exorheic catchments. We also compared the estimated regional ET with other ET products. Different precipitation products are assessed to explain the inconsistency between different ET products and regional ET from a water balance perspective. The RMSEs between ET estimates from Gravity Recovery and Climate Experiment (GRACE) and ET from land surface models can be reduced if the deviation of precipitation forcing data is considered. ET estimates from Global Land Evaporation Amsterdam Model (GLEAM) can be improved by reducing the uncertainty of precipitation forcing data in three semiarid catchments. This study emphasizes the importance of considering TWSC when calculating the regional ET using a water balance equation and provides more accurate ET estimates to help improve modeled ET results.

scholarly journals Terrestrial Water Storage Change Retrieved by GRACE and Its Implication in the Tibetan Plateau: Estimating Areal Precipitation in Ungauged Region

2020 ◽  
Vol 12 (19) ◽  
pp. 3129
Author(s):  
Yao Jia ◽  
Huimin Lei ◽  
Hanbo Yang ◽  
Qingfang Hu
Keyword(s):  
Tibetan Plateau ◽  
Water Balance ◽  
Balance Equation ◽  
Water Storage ◽  
The Tibetan Plateau ◽  
Terrestrial Water Storage ◽  
Water Balance Equation ◽  
Basin Scale ◽  
Terrestrial Water ◽  
Areal Precipitation

The Tibetan Plateau (TP) is referred to as the water tower of Asia, where water storage and precipitation have huge impacts on most major Asian rivers. Based on gravity recovery and climate experiment data, this study analyzed the terrestrial water storage (TWS) changes and estimated areal precipitation based on the water balance equation in four different basins, namely, the upper Yellow River (UYE), the upper Yangtze River (UYA), the Yarlung Zangbo River (YZ), and the Qiangtang Plateau (QT). The results show that the TWS change exhibits different patterns in the four basins and varies from −13 to 2 mm/year from 2003 to 2017. The estimated mean annual precipitation was 260 ± 19 mm/year (QT), 697 ± 26 mm/year (UYA), 541 ± 36 mm/year (UYE), and 1160 ± 39 mm/year (YZ) which performed better than other precipitation products in the TP. It indicates a potential method for estimating basin-scale precipitation through integrating basin average precipitation from the water balance equation in the poorly gauged and ungauged regions.

scholarly journals Water Balance Standardization Approach for Reconstructing Runoff Using GPS at the Basin Upstream

2020 ◽  
Vol 12 (11) ◽  
pp. 1767
Author(s):  
Hok Sum Fok ◽  
Linghao Zhou ◽  
Yongxin Liu ◽  
Robert Tenzer ◽  
Zhongtian Ma ◽  
...  
Keyword(s):  
Water Balance ◽  
Pearson Correlation ◽  
Water Storage ◽  
Remotely Sensed ◽  
River Delta ◽  
Mekong River ◽  
Time Shift ◽  
Mekong River Delta ◽  
Mekong Basin

While in-situ estuarine discharge has been correlated and reconstructed well with localized remotely-sensed data and hydraulic variables since the 1990s, its correlation and reconstruction using averaged GPS-inferred water storage from satellite gravimetry (i.e., GRACE) at the basin upstream based on the water balance standardization (WBS) approach remains unexplored. This study aims to illustrate the WBS approach for reconstructing monthly estuarine discharge (in the form of runoff (R)) at Mekong River Delta, by correlating the averaged GPS-inferred water storage from GRACE of the upstream Mekong Basin with the in-situ R at the Mekong River Delta estuary. The resulting R based on GPS-inferred water storage is comparable to that inferred from GRACE, regardless of in-situ stations within Mekong River Delta being used for the R reconstruction. The resulting R from the WBS approach with GPS water storage converted by GRACE mascon solution attains the lowest normalized root-mean-square error of 0.066, and the highest Pearson correlation coefficient of 0.974 and Nash-Sutcliffe efficiency of 0.950. Regardless of using either GPS-inferred or GRACE-inferred water storage, the WBS approach shows an increase of 1–4% in accuracy when compared to those reconstructed from remotely-sensed water balance variables. An external assessment also exhibits similar accuracies when examining the R estimated at another station location. By comparing the reconstructed and estimated Rs between the entrance and the estuary mouth, a relative error of 1–4% is found, which accounts for the remaining effect of tidal backwater on the estimated R. Additional errors might be caused by the accumulated errors from the proposed approach, the unknown signals in the remotely-sensed water balance variables, and the variable time shift across different years between the Mekong Basin at the upstream and the estuary at the downstream.

The drainage component of the water balance equation

Soil Research ◽  
1965 ◽  
Vol 3 (2) ◽  
pp. 95 ◽  
Author(s):  
CW Rose ◽  
WR Stern
Keyword(s):  
Water Balance ◽  
Water Content ◽  
Bulk Density ◽  
Balance Equation ◽  
Clay Soils ◽  
Swelling Clay ◽  
Water Balance Equation ◽  
Field Crops

A method is presented for determining the drainage term in the water balance equation, which may then be used to solve for evaporation from field crops. Questions concerning accuracy in determination of the drainage term are considered. Two special problems that arise in this context with swelling clay soils are discussed, namely, the variation of bulk density with water content, and the inference of in situ soil water suction from volumetric water content measurement.

scholarly journals Retention time of lakes in the Larsemann Hills oasis, East Antarctica

2020 ◽  
Author(s):  
Elena Shevnina ◽  
Ekaterina Kourzeneva ◽  
Yury Dvornikov ◽  
Irina Fedorova
Keyword(s):  
Water Balance ◽  
Retention Time ◽  
Balance Equation ◽  
Water Exchange ◽  
Warm Season ◽  
East Antarctica ◽  
Water Balance Equation ◽  
Larsemann Hills ◽  
Lake Volume ◽  
Field Campaigns

Abstract. The study gives first estimates of water transport scale for five lakes located in the Larsemann Hills oasis (69º23' S, 76º20' E) in the East Antarctica. We estimated the lake retention time (LRT) as a ratio of the lake volume to the income and outcome terms of a lake water balance equation. The LRT was evaluated for lakes of epiglacial and land-locked types, and it was assumed that these lakes are monomictic with water exchange existing during a warm season only. We used hydrological observations collected in 4 seasonal field campaigns to evaluate the LRT from the outcome and income terms of the water balance equation. For the epiglacial lakes Progress/LH57 and Nella/Scandrett/LH72, the LRT was estimated of 12–13 and 4–5 years, respectively. For the land-locked lakes Stepped/LH68, Sara Tarn/LH71 and Reid/LH70, our results show a big difference in the LRT calculated from the outcome and income components of the water balance equation. The LRT for these lakes vary depending on the methods and errors inherent to them. We suggested to rely on the estimations from the outcome surface runoff since they are based on the hydrological measurements with better quality. Lake Stepped/LH68 exchange water within less then 1.5 years. Lake Sara Tarn/LH71 and Lake Reid/LH70 are the endorheic ponds with the water exchange through mostly evaporation, their LRT was estimated as 21–22 years and from 8–9 years, respectively. To improve the estimates of the LRT, the hydrological observations are needed to monitor the lakes and streams during the warm season with the uniform observational program.

The Effectiveness of Evapotranspiration Systems in Disposing of Wastewater in Remote Aboriginal Communities in Northwest Australia

1991 ◽  
Vol 23 (10-12) ◽  
pp. 1825-1833
Author(s):  
D. R. McGrath ◽  
G. E. Ho ◽  
K. Mathew
Keyword(s):  
Water Balance ◽  
Water Loss ◽  
Balance Equation ◽  
Eucalyptus Camaldulensis ◽  
Bare Soil ◽  
Pan Evaporation ◽  
Aboriginal Communities ◽  
Water Balance Equation ◽  
Northwest Australia

The potential usage of Evapotranspiration (ET) systems in remote Aboriginal communities was investigated. ET system sizing requirements were determined from the water balance equation. Water loss from lysimeters planted with trees (Eucalyptus camaldulensis) or lawn grass and from bare soil and gravel was monitored over several months and compared to pan evaporation measured during the same period. It was found that ET from bare soil and grass followed similar trends to pan evaporation, ranging from 30-60% of pan evaporation for soil and from 60-80% of pan evaporation for grass. ET rates increased in the tanks planted with trees as the plants grew and exceeded pan evaporation rates. Evaporation from gravel-filled lysimeters was low, being as little as 10% of pan evaporation.

scholarly journals Global evapotranspiration over the past three decades: estimation based on the water balance equation combined with empirical models

2012 ◽  
Vol 7 (1) ◽  
pp. 014026 ◽  
Author(s):  
Zhenzhong Zeng ◽  
Shilong Piao ◽  
Xin Lin ◽  
Guodong Yin ◽  
Shushi Peng ◽  
...  
Keyword(s):  
Water Balance ◽  
Balance Equation ◽  
Empirical Models ◽  
Water Balance Equation ◽  
The Past
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