Paper accepted: Estimating the water budget components and their variability in a Pre-Alpine basin with JGrass-NewAGE

Finally our paper, on the water budget component estimation in the case where there are some in-situ observations  and when the area is dominated by snow, is accepted. Due to the complexities of issues involved and the tools needed, it has been two/three years since I started to work on this paper. When I say complexities, it mean that while the main goal is  one (i.e. water budget closure spatially, lets say each HRU), but the specific objectives are too many, i.e.

1. Comparison various interpolators/or if possible improve some of the approaches used in literature, with the objective to identify a method that provides more accurate rainfall fields.

2. When a basin is dominated by snow, you can not afford to ignore the snow process, and hence, how much of the total precipitation falling in the form of snowfall is really its own line of research. So we had to come up with some means to do this, and that was the second objective of the paper. 

3. The estimation of ET is problematic. In literature people uses the potential ET to estimate discharge, but most studies does not show actual ET. Hydrological studies are dominated by the rainfall-runoff exercise, with the aim to optimise discharge modelling to obtain high agreement with observed discharge.  From my experience, particularly gained from working on this paper, obtaining discharge estimation having good agreement with discharge observation does not require reasonable estimation of either potential ET or actual ET. Hence, modelling rainfall-runoff, without proper characterisation of ET, could not be the art of science in hydrology. so, the third objective is to estimate ET, which is consistent with the other water budget components.

4. Storage is probable the most difficult to estimate/model at basin scale, hence, the other specific objective of the paper is to develop a methodology for estimating storage at basin scale. 

It was started as two papers, but later we decided to compress them into one. This mean that we have to cut out many results and issues. All this processes took time. In anyway, if you are interested, please find the accepted manuscript here.  

Quantifying groundwater or terrestrial water storage using GRACE

The use of GRACE data for hydrological models to quantify the terrestrial water balance is a way to approach the large body of unknown knowledge of the water storage function. While the use of models and meteorological data helps to estimate most of the water balance components with some reasonable confidence, the quantification of the storage is very difficult, and such supporting data is clearly improve the estimations particularly in large basins. Sooner or later, in the line of water balance estimation at large scale basin, the use of GRACE will be my research agenda. I came across to this paper which shows some approach how to include the GRACE data in the basin water balance modelling.   The abstract reads as:

"Groundwater is an increasingly important water supply source globally. Understanding the amount of groundwater used versus the volume available is crucial to evaluate future water availability. We present a groundwater stress assessment to quantify the relationship between groundwater use and availability in the world’s 37 largest aquifer systems. We quantify stress according to a ratio of groundwater use to availability, which we call the Renewable Groundwater Stress ratio. The impact of quantifying groundwater use based on nationally reported groundwater withdrawal statistics is compared to a novel approach to quantify use based on remote sensing observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. Four characteristic stress regimes are defined: Overstressed, Variable Stress, Human-dominated Stress, and Unstressed. The regimes are a function of the sign of use (positive or negative) and the sign of groundwater availability, defined as mean annual recharge. The ability to mitigate and adapt to stressed conditions, where use exceeds sustainable water availability, is a function of economic capacity and land use patterns. Therefore, we qualitatively explore the relationship between stress and anthropogenic biomes. We find that estimates of groundwater stress based on withdrawal statistics are unable to capture the range of characteristic stress regimes, especially in regions dominated by sparsely populated biome types with limited cropland. GRACE-based estimates of use and stress can holistically quantify the impact of groundwater use on stress, resulting in both greater magnitudes of stress and more variability of stress between regions."

some references (to be updated ):

Van Dijk, A. I. J. M., L. J. Renzullo, and M. Rodell. "Use of GRACE terrestrial water storage retrievals to evaluate model estimates by the Australian water resources assessment system." Water Resour. Res 47 (2011): W11524.

Kirk Zmijewski and Richard Becker, 2014: Estimating the Effects of Anthropogenic Modification on Water Balance in the Aral Sea Watershed Using GRACE: 2003–12. Earth Interact., 18, 1–16. doi: http://dx.doi.org/10.1175/2013EI000537.1

Deus D, Gloaguen R, Krause P. Water Balance Modeling in a Semi-Arid Environment with Limited in situ Data Using Remote Sensing in Lake Manyara, East African Rift, Tanzania. Remote Sensing. 2013; 5(4):1651-1680.

van Dijk, A. I. J. M., et al. "A global water cycle reanalysis (2003–2012) merging satellite gravimetry and altimetry observations with a hydrological multi-model ensemble." (2014).

Eunjin Han, Wade T. Crow, Christopher R. Hain, and Martha C. Anderson, 2015: On the Use of a Water Balance to Evaluate Interannual Terrestrial ET Variability. J. Hydrometeor, 16, 1102–1108. doi: http://dx.doi.org/10.1175/JHM-D-14-0175.1

Scanlon, B. R., L. Longuevergne, and D. Long (2012), Ground referencing GRACE satellite estimates of groundwater storage changes in the California Central Valley, USA, Water Resour. Res., 48, W04520, doi:10.1029/2011WR011312.