GRACE-derived seasonal variations, a key to understanding aquifer sources, recharge and groundwater flow patterns

2020 ◽  
Author(s):  
karem Abdelmohsen ◽  
Mohamed Sultan ◽  
Himanshu Save
Keyword(s):  
Groundwater Flow ◽  
Seasonal Variations ◽  
Spherical Harmonic ◽  
Land Surface ◽  
Land Surface Model ◽  
Buffer Zone ◽  
Forward Modeling ◽  
Surface Model ◽  
Aquifer System ◽  
Lake Nasser

<p>The Nubian Sandstone Aquifer System (NSAS) in northeast Africa is formed of three subbasins, the Dakhla, Kufra, and the Northern Sudan Platform subbasins. The Dakhla subbasin (DSB) receives negligible precipitation (<10 mm/yr), yet displays significant seasonal variations in GRACETWS (average: 50 mm/yr, up to 77 mm/yr) across the entire subbasin. The origin of these variations could be related to one or more of the following factors: (1) leakage out from Lake Nasser, (2) leakage in from surroundings (Kufra basin [west NSAS], Northern Sudan Platform [south NSAS], Mediterranean sea [north NSAS], and Red Sea [east NSAS], and (3) recharge and rapid groundwater flow from Lake Nasser and the northern Sudan Platform. Three approaches were used to investigate the contribution of leakage (factors 1 and 2) to the observed GRACETWS signal over the DSB subbasin: (1) forward modeling (in spherical harmonic domain) of the maximum variations in Lake Nasser levels was applied to test whether the observed seasonal variation in GRACETWS across the DSB can be accounted for by leakage from Lake Nasser alone; (2) estimate (in spherical harmonic domain) the leakage in signal using the simulated TWS from the widely applied Land Surface Model (LSM), GLDAS (Global Land Data Simulation System); and (3) apply iterative forward modeling (iterations: n=30) to reconstruct the true mass variations of GRACETWS over the DSB. Findings suggest: (1) the leakage in signal over the DSB cannot account for the observed seasonal GRACETWS patterns and neither can the leakage out from Lake Nasser; (2) the leakage out signal is centered over Lake Nasser and extends to its immediate surroundings with a maximum radius of 250 km (upper boundary of leakage error); (3) the iterative modeling indicates that the maximum leakage within the 250 km buffer zone around the lake amounted to 22.6 % of the observed GRACETWS signal; (4) minimal leakage (up to 10 mm) from northerly precipitation is observed along the northern sections (~200 km deep) of the NSAS and negligible (< 4 mm) leakage is detected over the remaining sections of the DSB; and (5) the observed seasonal variations in GRACETWS over the DSB is related to an increase in groundwater storage related to seasonal recharge from Lake Nasser and rapid groundwater flow along a network of faults, fractures, and karst topography across the entire DSB.</p>

scholarly journals Simulating precipitation decline under a Mediterranean deciduous Oak forest: effects on isoprene seasonal emissions and predictions under climatic scenarios

2017 ◽  
Author(s):  
Anne-Cyrielle Genard-Zielinski ◽  
Christophe Boissard ◽  
Elena Ormeño ◽  
Juliette Lathière ◽  
Ilja M. Reiter ◽  
...  
Keyword(s):  
Water Stress ◽  
Seasonal Variations ◽  
Land Surface ◽  
Environmental Changes ◽  
Seasonal Pattern ◽  
Land Surface Model ◽  
Surface Model ◽  
Emission Rates ◽  
Drought Intensity ◽  
Isoprene Emission

Abstract. Seasonal variations of Q. pubescens physiology and isoprene emission rates (ER) were studied from June 2012 to June 2013 at the O3HP site (French Mediterranean) under natural (ND) and amplified (+30 %, AD) drought. While AD significantly reduced the stomatal conductance to water vapour over the season excepting August, it did not significantly limit CO2 net assimilation, which was the lowest in summer. ER followed a significant seasonal pattern, whatever the drought intensity, with mean ER maxima of 78.5 and 104.8 µgC gDM−1 h−1 in July (ND) and August (AD) respectively. Isoprene emission factor increased significantly by a factor of 2 in August and September under AD (137.8 and 74.3 µgC gDM−1 h−1) compared to ND (75.3 and 40.21 µgC gDM−1 h−1), but no changes occurred on ER. An isoprene algorithm (G14) was developed using an optimised artificial neural network trained on our experimental dataset (ER + O3HP climatic and edaphic parameters cumulated over 0 to 21 days before measurements). G14 assessed more than 80 % of the observed ER seasonal variations, whatever the drought intensity. In contrast, ER was poorly assessed under water stress by MEGAN empirical isoprene model, in particular under AD. Soil water (SW) content was the dominant parameter to account for the observed ER variations, regardless the water stress treatment. ER was more sensitive to higher frequency environmental changes under AD (0 to −7 days) compared to ND (7 days). Using IPCC RCP2.6 and RCP8.5 climate scenarios, SW and temperature calculated by the ORCHIDEE land surface model, and G14, an annual 3 fold ER relative increase was found between present (2000–2010) and future (2090–2100) for RCP8.5 scenario compared to a 70 % increase for RCP2.6. Future ER remained mainly sensitive to SW (both scenarios) and became dependent to higher frequency environmental changes under RCP8.5.

scholarly journals A high resolution global scale groundwater model

2014 ◽  
Vol 11 (5) ◽  
pp. 5217-5250 ◽  
Author(s):  
I. E. M. de Graaf ◽  
E. H. Sutanudjaja ◽  
L. P. H. van Beek ◽  
M. F. P. Bierkens
Keyword(s):  
Groundwater Flow ◽  
Land Surface ◽  
Regional Scale ◽  
Land Surface Model ◽  
Global Scale ◽  
Water Levels ◽  
Natural State ◽  
Surface Model ◽  
Groundwater Model ◽  
Aquifer Systems

Abstract. Groundwater is the world's largest accessible source of fresh water. It plays a vital role in satisfying needs for drinking water, agriculture and industrial activities. During times of drought groundwater sustains baseflow to rivers and wetlands, thereby supporting ecosystems. Most global scale hydrological models (GHMs) do not include a groundwater flow component, mainly due to lack of geohydrological data at the global scale. For the simulation of lateral flow and groundwater head dynamics a realistic physical representation of the groundwater system is needed, especially for GHMs that run at finer resolution. In this study we present a global scale groundwater model (run at 6' as dynamic steady state) using MODFLOW to construct an equilibrium water table at its natural state as the result of long-term climatic forcing. The aquifer schematization and properties were based on available global datasets of lithology and transmissivities combined with estimated aquifer thickness of an upper unconfined aquifer. The model is forced with outputs from the land-surface model PCR-GLOBWB, specifically with net recharge and surface water levels. A sensitivity analysis, in which the model was run with various parameter settings, showed variation in saturated conductivity causes most of the groundwater level variations. Simulated groundwater heads were validated against reported piezometer observations. The validation showed that groundwater depths are reasonably well simulated for many regions of the world, especially for sediment basins (R2 = 0.95). The simulated regional scale groundwater patterns and flowpaths confirm the relevance of taking lateral groundwater flow into account in GHMs. Flowpaths show inter-basin groundwater flow that can be a significant part of a basins water budget and helps to sustain river baseflow, explicitly during times of droughts. Also important aquifer systems are recharged by inter-basin groundwater flows that positively affect water availability.

scholarly journals Coupling a groundwater model with a land surface model to improve water and energy cycle simulation

2012 ◽  
Vol 9 (1) ◽  
pp. 1163-1205 ◽  
Author(s):  
W. Tian ◽  
X. Li ◽  
X.-S. Wang ◽  
B. X. Hu
Keyword(s):  
Groundwater Flow ◽  
Land Surface ◽  
Flow Model ◽  
Land Surface Model ◽  
Coupled Model ◽  
Subsurface Water ◽  
Surface Model ◽  
Groundwater Flow Model ◽  
Groundwater Model ◽  
Depth Zone

Abstract. The water and energy cycles interact, making them generally closely related. Land surface models (LSMs) can describe the water and energy cycles of the land surface, but their description of the subsurface water processes is oversimplified, and lateral groundwater flow is ignored. Groundwater models (GWMs) well describe the dynamic movement of subsurface water flow, but they cannot depict the physical mechanism of the evapotranspiration (ET) process in detail. In this study, a coupled model of groundwater with simple biosphere (GWSiB) is developed based on the full coupling of a typical land surface model (SiB2) and a three-dimensional variably saturated groundwater model (AquiferFlow). In this model, the infiltration, ET and energy transfer are simulated by SiB2 via the soil moisture results given by the groundwater flow model. The infiltration and ET results are applied iteratively to drive the groundwater flow model. The developed model is then applied to study water cycle processes in the middle reaches of the Heihe River Basin in the northwest of China. The model is validated through data collected at three stations in the study area. The stations are located in a shallow groundwater depth zone, a deeper groundwater depth zone and an agricultural irrigation area. The study results show that the coupled model can well depict the land surface and groundwater interaction and can more comprehensively and accurately simulate the water and energy cycles compared with uncoupled models.

scholarly journals Evaluation of Groundwater Simulations in Benin from the ALMIP2 Project

2019 ◽  
Vol 20 (2) ◽  
pp. 339-354
Author(s):  
Mehnaz Rashid ◽  
Rong-You Chien ◽  
Agnès Ducharne ◽  
Hyungjun Kim ◽  
Pat J.-F. Yeh ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Surface Runoff ◽  
Land Surface ◽  
Water Budget ◽  
Land Surface Model ◽  
Substantial Improvement ◽  
Base Flow ◽  
Specific Yield ◽  
Surface Model ◽  
Multidisciplinary Analysis

AbstractA comprehensive estimation of water budget components, particularly groundwater storage (GWS) and fluxes, is crucial. In this study, we evaluate the terrestrial water budget of the Donga basin (Benin, West Africa), as simulated by three land surface models (LSMs) used in the African Monsoon Multidisciplinary Analysis Land Surface Model Intercomparison Project, phase 2 (ALMIP2): CLM4, Catchment LSM (CLSM), and Minimal Advanced Treatments of Surface Interaction and Runoff (MATSIRO). All three models include an unconfined groundwater component and are driven by the same ALMIP2 atmospheric forcing from 2005 to 2008. Results show that all three models simulate substantially shallower water table depth (WTD) with smaller seasonal variations, approximately 1–1.5 m compared to the observed values that range between 4 and 9.6 m, while the seasonal variations of GWS are overestimated by all the models. These seemingly contradictory simulation results can be explained by the overly high specific yield prescribed in all models. All models achieve similar GWS simulations but with different fractions of precipitation partitioning into surface runoff, base flow, and evapotranspiration (ET), suggesting high uncertainty and errors in the terrestrial and groundwater budgets among models. The poor performances of models can be attributed to bias in the hydrological partitioning (base flow vs surface runoff) and sparse subsurface data. This analysis confirms the importance of subsurface hydrological processes in the current generation of LSMs and calls for substantial improvement in both surface water budget (which controls groundwater recharge) and the groundwater system (hydrodynamic parameters, vertical geometry).

scholarly journals Coupling a groundwater model with a land surface model to improve water and energy cycle simulation

2012 ◽  
Vol 9 (9) ◽  
pp. 10917-10962 ◽  
Author(s):  
W. Tian ◽  
X. Li ◽  
G.-D. Cheng ◽  
X.-S. Wang ◽  
B. X. Hu
Keyword(s):  
Groundwater Flow ◽  
Land Surface ◽  
Flow Model ◽  
Land Surface Model ◽  
Coupled Model ◽  
Groundwater Depth ◽  
Subsurface Water ◽  
Surface Model ◽  
Groundwater Flow Model ◽  
Groundwater Model

Abstract. Water and energy cycles interact, making these two processes closely related. Land surface models (LSMs) can describe the water and energy cycles on the land surface, but their description of the subsurface water processes is oversimplified, and lateral groundwater flow is ignored. Groundwater models (GWMs) describe the dynamic movement of the subsurface water well, but they cannot depict the physical mechanisms of the evapotranspiration (ET) process in detail. In this study, a coupled model of groundwater flow with a simple biosphere (GWSiB) is developed based on the full coupling of a typical land surface model (SiB2) and a three-dimensional variably saturated groundwater model (AquiferFlow). In this coupled model, the infiltration, ET and energy transfer are simulated by SiB2 using the soil moisture results from the groundwater flow model. The infiltration and ET results are applied iteratively to drive the groundwater flow model. After the coupled model is built, a sensitivity test is first performed, and the effect of the groundwater depth and the hydraulic conductivity parameters on the ET are analyzed. The coupled model is then validated using measurements from two stations located in shallow and deep groundwater depth zones. Finally, the coupled model is applied to data from the middle reaches of the Heihe River basin in the northwest of China to test the regional simulation capabilities of the model.

scholarly journals Coupling a groundwater model with a land surface model to improve water and energy cycle simulation

2012 ◽  
Vol 16 (12) ◽  
pp. 4707-4723 ◽  
Author(s):  
W. Tian ◽  
X. Li ◽  
G.-D. Cheng ◽  
X.-S. Wang ◽  
B. X. Hu
Keyword(s):  
Groundwater Flow ◽  
Land Surface ◽  
Flow Model ◽  
Land Surface Model ◽  
Coupled Model ◽  
Groundwater Depth ◽  
Subsurface Water ◽  
Surface Model ◽  
Groundwater Flow Model ◽  
Groundwater Model

Abstract. Water and energy cycles interact, making these two processes closely related. Land surface models (LSMs) can describe the water and energy cycles on the land surface, but their description of the subsurface water processes is oversimplified, and lateral groundwater flow is ignored. Groundwater models (GWMs) describe the dynamic movement of the subsurface water well, but they cannot depict the physical mechanisms of the evapotranspiration (ET) process in detail. In this study, a coupled model of groundwater flow with a simple biosphere (GWSiB) is developed based on the full coupling of a typical land surface model (SiB2) and a 3-D variably saturated groundwater model (AquiferFlow). In this coupled model, the infiltration, ET and energy transfer are simulated by SiB2 using the soil moisture results from the groundwater flow model. The infiltration and ET results are applied iteratively to drive the groundwater flow model. After the coupled model is built, a sensitivity test is first performed, and the effect of the groundwater depth and the hydraulic conductivity parameters on the ET are analyzed. The coupled model is then validated using measurements from two stations located in shallow and deep groundwater depth zones. Finally, the coupled model is applied to data from the middle reach of the Heihe River basin in the northwest of China to test the regional simulation capabilities of the model.

L'apport de la télédétection spatiale à la modélisation des surfaces continentales

2020 ◽  
pp. 052
Author(s):  
Jean-Christophe Calvet ◽  
Jean-Louis Champeaux
Keyword(s):  
Satellite Data ◽  
Land Surface ◽  
Land Surface Model ◽  
Static Model ◽  
Geographic Information ◽  
Surface Model ◽  
Model Parameters

Cet article présente les différentes étapes des développements réalisés au CNRM des années 1990 à nos jours pour spatialiser à diverses échelles les simulations du modèle Isba des surfaces terrestres. Une attention particulière est portée sur l'intégration, dans le modèle, de données satellitaires permettant de caractériser la végétation. Deux façons complémentaires d'introduire de l'information géographique dans Isba sont présentées : cartographie de paramètres statiques et intégration au fil de l'eau dans le modèle de variables observables depuis l'espace. This paper presents successive steps in developments made at CNRM from the 1990s to the present-day in order to spatialize the simulations of the Isba land surface model at various scales. The focus is on the integration in the model of satellite data informative about vegetation. Two complementary ways to integrate geographic information in Isba are presented: mapping of static model parameters and sequential assimilation of variables observable from space.

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