Estimating water budget of large basin with NewAge-JGrass

This paper has been out there for a year, as discussion paper in HESS. After a long review process, now it is accepted. Most of the issues and discussions are almost similar to the discussion paper. However, discussion and the methodology sections have been improved a lot in the final and accepted paper.  It is open access meaning it can be accessed for any one at this link.

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.  

Evapotranspiration

From 7-11 of November, 2016, I attended an international symposium on ecohydrology in Africa. It is the 2nd African international symposium on ecohydrology for water and ecosystem service, and it seems that the symposium has a back from the political officials with the aim to establish an Ecohydrological centre at Addis Ababa. There were many interesting presentations, with different case studies. The list of presentations and the downloadable slides is available at http://ehsymposiumafrica.org/programme-symposium-africa/

My presentation was  on the methods to estimate basin scale evapotranspiration, eventually water budget. Here you can find my slides.

Wuletawu Abera, presentation on basin scale evapotranspiration, at "ecohydrology in Africa" Symposium (photo credit: Professor Zalewski)

Water Budget of the upper Blue Nile basin

If we, as a hydrologic science community,  are aims to contribute for understanding and managing  the water resource, it is important to provide space-time information for all the components of water cycle i.e precipitation, evapotranspiration, runoff, and storage together. Usually such estimation is persuaded at annual time scale for large basin using the budyko hypothesis. However,  this kind of estimation is not useful for operational purpose as hydrological information at daily and weekly scale is a key for agricultural application. Here, a paper submitted for HESSD, is our  effort to estimate  space-time distributed water budget for the Upper Blue Nile basin, an exemplary for data scarce and large scale problems.

On the total freshwater storage deficit of Ethiopia

As it receives one of the highest rainfall amount in the continent and the region,  Ethiopia is the water tower for the greater horn of Africa and the Nile. Because of its small-holder and traditional based  agrarian economy, but recurrent drought is the main development challenge. In the last decades, hydrologists developed  many drought indexes based on various hydrological and meteorological components like rainfall, evapotranspiration, and runoff to provide indexes for decision making. some of these are: Drought Severity Index (PDSI) (Palmer, 1965), Crop Moisture Index (CMI) (Palmer, 1968), Standardized Precipitation Index (SPI) (McKee et al., 1993), and Surface Water Supply Index (SWSI) (Shafer and Dezman, 1982). There are already  some efforts  to  understand the pattern of rainfall in the region,  mainly from the long term climate change perspective, and the findings are mixed.

The total available freshwater is the residual of all the hydrological fluxes. Hence, it is the integrated indicator of the water budget system of a basin.  On the contrary,  it  is the most difficult component to measure, if obtained with huge efforts, it is very specific and point information. NASA’s Gravity Recovery and Climate Experiment (GRACE) mission (Tapley et al., 2004) provides an independent satellite observation of change of the total water storage. Recently this data has been used to estimate the total water deficit of large basin, and it is evaluated positively. Here, I analyzed GRACE data to understand the total water storage of the Ethiopia. The objectives are:1. to estimate the long term water storage mean at monthly time steps; 2. to estimate the total water deficit of each months ("drought event" if longer than the months ); 3. to calculate the total water status according to the GRACE observation for the last one decade.Here are some results, and hoping to detail the methodology and extend the results in the near future. 

Fig 1: The long term mean monthly total water storage distribution of Ethiopia according to GRACE observation.

Fig 2: the long term monthly mean storage deficit maps of Ethiopia as observed from GRACE

Fig: Time series storage deficit (below zero ) at national level . At national scale, the water storage over the long term trend is more or less at constant level

 Fig 4: the time series storage deficit at four location in the country 

To be continued…..

References 

Palmer, W.C. Meteorological Drought; U.S. Department of Commerce, Weather Bureau: Washington, DC, USA, 1965. 

Shafer, B.A.; Dezman, L. Development of a Surface Water Supply Index (SWSI) to assess the severity of drought conditions in snowpack runoff Areas. In Proceedings of the Western Snow Conference, Reno, NV, USA, 19–23 April 1982. 

McKee, T.B., Doesken, N.J., Kleist, J., 1993. The relationship of drought frequency and duration to time scales. In: Proceedings of the 8th Conference on Applied Climatology, American Meteorological Society, Anaheim, CA, Boston, MA, 17–22 January, pp. 179–184.

Tapley, B. D., S. Bettadpur, J. C. Ries, P. F. Thompson, and M. M. Watkins (2004), GRACE measurements of mass variability in the Earth system, Science, 305(5683), 503–505, doi:10.1126/science.1099192.

AboutHydrology: Wuletawu's Abera Ph.D. defense

AboutHydrology: Wuletawu's Abera Ph.D. defense: This illustrate the long and detailed work of Wuletawu Abera during his Ph.D. His topic was modelling the whole hydrological cycle, meaning...

EGU Topical conference

This year, three important meetings of water science  jointly organised at Addis Ababa, from November 18-20, 2015.  The three meetings are the Alexander von Humboldt Conference of the European Geosciences Union, the STAHY workshop of the International Commission on Statistical Hydrology of the International Association of Hydrological Sciences (ICSH-IAHS) and the Leonardo Conference of the Hydrological Sciences Division of the European Geosciences Union. While there were a lot of good presentation, the following three presentations were more interesting topics of  basin water balance modelling  in general and our (my) approach of doing water balance estimation in particular. 

• Towards Optimization of Reservoir Operations for Hydropower Production in East Africa: Seasonal Climate Forecasts (Leonardo Lecture) --- by Mekonnen Gebremichael. Abstract 
• Education and TAHMO, the Trans-African Hydro-Meteorological Observatory --- by Nick van de Giesen. Abstract  
• How important are soils for hydrological modelling?  --- by Hubert H.G. Savenije. Abstrac 
• characterisation of the regional variability of seasonal water balances within the Omo-Gibe River basin --- by Adanech Yared Jillo 

I had two presentations: One on the comparison of satellite rainfall estimation products for the purpose of basin water balance modelling inputs, and the second was a work in progress on JGrass-NewAge set-up for water balance estimation in Upper Blue Nile basin.  The abstract can be found here and here, respectively. A video of  one of the my presentation (or a part of it) is recorded by my friend and can also be found in this you tube. 

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.

The innovative use of satellites to predict famine

This is really interesting achievement of Gabriel Senay. Besides to his breakthrough researches and studies, he is one of Ethiopian hydrologist tries to apply his research for practical problems. I do't have much exposure, except few, to his researches and studies,  but I would like to know more.   Anyway I have seen this long description by SMITHSONIAN MAGAZINE  about him and his researches in Ethiopia at this magazine. The innovative use of satellites to predict famine

Gabriel Senay in his office (source: SMITHSONIAN MAGAZINE )

Very interesting paper on basin water yields

The very idea of budyko curve and other long term water balance approach is to characterise the basin water yeild capacity, or, the capacity of the basin to generate the discharge at the outlet, for a given precipitation. In other words, how the basin is parttioning the incoming inputs, rainfall, into different outflow (i.e ET and Q). In most studies, the formulations, the main driver that is asumed and explicitly accounted, is the basin energy-budget, in the form of PET. For me, though I didn't review literatures very well, it seems that the mere description and formulation of precipitaion, P, and potentail evapotranspiration, PET, would not explian the dischrage, Q, specially in the so-called a single hydrological year and so. I find that this (Zhou et al)\( ^{1} \) paper published in NATURE COMMUNICATIONS, and, is very promising with easy analytical formulation.
From the simplified water balance equation \[ P=E+R+ \Delta S \] where P is rainfall, E is evapotranspiration, and R runoff and \( \Delta S \) change in storage differences for a given hydrological year. Assuming the \( \Delta S = 0 \) for a given hydrological year, or even better for longer hydrological years, after re-arranging the equation will be:
\[ \frac{R}{P} = 1-\frac{E}{P} \]
From this point, there are some studies on how to estimate the \( E \) from the \( P \) and \( PET \) (e.g. Zeng and Cai, 2015\( ^{3} \) and papers cited therein), defines \( E \) as function of aridity index (\( PET/P \)), \[ E= P(1+ \frac{PET}{P} - (1+(\frac{PET}{P})w)^{\frac{1}{w}})) \]
This \( E \) formulation is substituted, and the reciprocal of the aridity index (\( P/PET \)), wetnes index, is used for analytical simplicity , i.e:
\[ \frac{R}{P}=(1+ (\frac{P}{PET})^{-m})^{\frac{1}{m}}-(\frac{P}{PET})^{-1} \]
which relates annual water yield ( R ) to a wetness index (precipitation/ potential evapotranspiration; P/PET) and watershed characteristics (m). m could be connected to many watershed characterstics, such as soil, vegetation, basin area, geomorphometry.

There is also an intersting efforts by Voepel et'al\( ^{2} \) on the controls of hydrologic partitioning at the catchment scale. One important thing in thier approach is the way they concptualize basin wetting and aridity in relation to the Normalized Difference Vegetation Index (NDVI). This would make the job easy, because it is easy to use NDVI from satellite.
Anyways, what interest me is \( m \) can be assessed with wide ranges of basin characterstics, and, further refine the equation with the dominante physical paramater(s).
References

1. \( ^{1} \) Guoyi Zhou, Xiaohua Wei, Xiuzhi Chen1, Ping Zhou, Xiaodong Liu, Yin Xiao, Ge Sun, David F. Scott, Shuyidan Zhou, Liusheng Han & Yongxian Su: Global pattern for the effect of climate and land cover on water yield.“ Nature Communications 6, Article number: 5918 DOI: 10.1038/ncomms6918
2. \( ^{2} \)Voepel, H., B. Ruddell, R. Schumer, P. A. Troch, P. D. Brooks, A. Neal, M. Durcik, and M. Sivapalan (2011), Quantifying the role of climate and landscape characteristics on hydrologic partitioning and vegetation response, Water Resour. Res., 47, W00J09, doi:10.1029/2010WR009944.
3. \( ^{3} \)Ruijie Zeng, Ximing Cai. (2015) Assessing the temporal variance of evapotranspiration considering climate and catchment storage factors. Advances in Water Resources 79, 51-60.
4. Gerrits, A. M. J., H. H. G. Savenije, E. J. M. Veling, and L. Pfister (2009), Analytical derivation of the Budyko curve based on rainfall characteristics and a simple evaporation model, Water Resour. Res., 45, W04403, doi:10.1029/2008WR007308

consultant and business idea

Apart from the research and academia world, if I would like to work (establish) consultant and business  out of my professional life, at least for the sake of supporting my research career, I would go for something like  eWaterCycle project. Since I am working on the water balance at smallest subbasin scale, my Professor brought this project to my attention. From their website,  eWaterCycle   " is a project that will provide detailed hydrological information for water management challenges around the globe. We will calculate how much water is available in each part of the world at present and in the near future". 

The ultimate objective of hydrology as a subject and hydrologist as a profession is to understand the hydrological processes to estimate the available water at different scales.  Hence, it feels for me that organising ones work for the sake of this objective will always have practical and professional career.