I read this in a LinkedIn discussion, and I found it the perfect complement of my previous post "Essential for Hydrologists"
Question:
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Question:
Hello,
I have a question specified in the following and hope some of you can guide me a
bit:
There is a lake which is the source of water for an industrial project. The project is known for being water intensive, approximately 20 tons fresh water is needed for production of 1 ton final product. According to satellite images, the lake area has been shrinking for approximately 62% since the project started operation about 5 years ago. Local farmers also complained that they had to dig water as deep as 100 meters in order to get water, indicating a severe drop of ground water level. We would like to know quantitatively how water extraction has caused local water scarcity problem. I wonder whether we need a hydrological model to do such assessment; if a hydrological model is not available for that specific lake, is that possible use time series data to run a regression model where lake area is seen as a function of water extraction, precipitation, temperature, etc.
I wonder how analysis like is done typically, if any of you is aware of any exisiting studies, please do let me know. Many thanks in advance.
Best wishes
Sissi
Answer:
Dear Sissi,
Five year data is not adequate for detailed analysis. The reason of decline is due to inadequate rainfall in these five years or increase of draft for different purposes during the five year. Recently I have done a similar study in one of the lakes in India, though not for the same purpose. I would like to suggest the following points.
1. Study the rainfall / inflow pattern for at least for 50 years
2. Use the Soil and Water Assessment Tool (SWAT)and estimate the water balance taking the rainfall and temperature and other data for at least 15 year daily data.
3. If you have actual inflow data, compare the results with the actual inflow data.
4. If you do not have actual inflow data, asses the inflow by SCS-CN Method (Soil Conservation services (SCS), HEC_HMS and compare the data with SWAT.
5. Use HEC-RAS and HEC-GEORAS for flood modelling if required to delineate the areas of flood in the lake catchment.
.........
With best wishes,
**
My comment:
The answer is certainly correct. HEC* and SWAT constitute very well engineered standard models used in operational (and operative) hydrology. SCS-CN method, was already commented. Certainly a term of reference. However, if you look at the physics under the hood, you can recognise the existence of many of those "old-style" parameterisations and simplifications that I tried to avoid in favour of more physically sound choices in GEOtop, more modernity, both in the way to implement the model solutions and the way to do simplifications, in JGrass-NewAGE and my lectures in hydrology.
Therefore the answer is perfect if you have to do (possibly is also perfect if you, at the end are an engineer) but I feel uncomfortable with it. Can't we do it better ?