Application I – Estimation of Groundwater Pumping
6.5 Appendix 5: Comments on March 15, 2013 Draft Report, Submitted by Dr. Sivakumaran with
6.5.1 Comments by Dr. Kumarswamy Sivakumaran
My observations from the workshop:
(a) The model developers are concerned that certain “unfavorable” comments may lead their management to find fault with them.
(b) The review has extensively covered the theoretical, numerical, and computational factors.
If I were a manager and would like to choose a model, I would like to have the following questions answered by the model developers:
Please answer the following questions for a hypothetical catchments or basin of area 500 square miles:
(i) What is the minimum qualification needed for a person to use the computer code?
(ii) What areas of expertise do the modelers need?
(iii) Do they need to be experts in Arc GIS?
(iv) Do they need prior experience in the models before using them? If so, how many years?
(v) If prior experience is not necessary, how much time will it take for someone to learn, knowing that people learn at different rates?
(vi) Does the modeler need any other support staff? If so, how many and what areas of expertise should they have?
(vii) How much time is needed to assemble the data for each of the models?
(viii) How much time needs to be spent on calibrating and verifying the model before it is used for predictions?
(Note: I am using the terms models and codes as synonyms)
6.5.2 Response to Comments provided by the DWR IWFM team
.DWR Responses to Questions by Dr. Kumarswamy Sivakumaran as Part of the 2012-2013 CWEMF Peer Review Process of Ground Water Models (7-5-2013)
We appreciate the questions raised by Dr. Sivakumaran as they point to many important issues related to use of computerized mathematical models to address real world water resources related management and planning issues. Our responses below will be limited and based on our own experiences with IWFM and its applications and hopefully provide answers sought to the questions asked.
How IWFM is used in a specific project is very much dependent on where the model is applied and what answers are being sought, and what options/capabilities within IWFM are used to obtain those answers.
For example: is the application pure ground water flow? Are there streams and canals to consider stream/aquifer interaction? Are there agricultural and urban water demands? Are they processed
elsewhere, or is IWFM used to develop land-use based water demands? Is IWFM being used for a historical simulation or a planning simulation? Is the model being used to balance supply and demand components? In the responses below it will be assumed that most of the capabilities of IWFM will be used including deriving agricultural/urban land-use based demands similar to many applications already under way in California and Oregon.
Two types of IWFM users will be considered:
User Type A that develops an IWFM application from scratch, calibrates it, and uses it to develop scenarios to answer hydrologic questions.
User Type B that obtains an already calibrated IWFM application and uses it to develop scenarios to answer hydrologic/management questions. Both of these user types are common in real-world and they need different qualifications to be able to use IWFM.
(i) What is the minimum qualification needed for a person to use the computer code?
User Type A:
Since IWFM is an integrated hydrologic model that simulates many components of the hydrologic cycle and the interactions between these components, it requires the user to have: a good background in surface water – ground water hydrology and modeling, and an in-depth knowledge on the dynamics of many runoff processes as well as the farming and irrigation practices and how these practices might affect the natural flow patterns. The input data development requires a moderate proficiency in ArcGIS, Excel and a sophisticated text editor such as Textpad. Knowledge of NRCS SSURGO soils database and on how to process this database will be needed in developing the parameters for the root zone flow processes. Calibration of an IWFM application can be done manually or automated depending on the number of parameters being calibrated. In general, knowledge of automated parameter estimation software such as PEST or UCODE will be useful.
User Type B:
A user who obtains an already calibrated IWFM application to do scenario runs needs to have a basic understanding of the dynamics of the hydrologic cycle and the interactions between its components.
They also need to have an understanding of how farming and irrigation practices may affect the natural flow patterns. To be able to develop scenarios and interpret the simulation results, the user needs to know how to manipulate columnar text data and moderate Excel functionality. IWFM produces many optional output data that allows the user to analyze the simulation results without having to “intercept” the source code. Although knowledge of ArcGIS is useful, it is not required for User Type B.
(ii) What areas of expertise do the modelers need?
User Type A:
A good grasp of principles in surface water hydrology, ground water hydrology (hydrogeology), and numerical modeling is recommended, typically found in an engineering (water resources), or hydrological sciences academic background. A basic understanding of irrigation engineering
principals and soil science, expertise in software such as ArcGIS, Excel, Textpad, PEST or UCODE is highly desired.
User Type B:
A general background in surface water and ground water hydrology, a basic understanding of irrigation engineering principles, a grasp of basic numerical modeling concepts, and moderate ability to use software such as Excel and Textpad is recommended.
(iii) Do they need to be experts in ArcGIS?
User Type A:
No, but a basic knowledge of ArcGIS would be very useful.
User Type B:
No.
(iv) Do they need prior experience in the models before using them? If so, how many years?
User Type A:
A user with experience with any hydrologic modeling software can quickly pick up IWFM. Our experience in helping other users suggests that within a 2 to 4-week period users that have no knowledge of IWFM start using it effectively due to its intuitive input and output data file structure.
User Type B:
Similar to User Type A, User Type B will only need a 2 to 4-week period to get up to speed with IWFM.
(v) If prior experience is not necessary, how much time will it take for someone to learn, knowing that people learn at different rates?
Please see the response for item (iv).
(vi) Does the modeler need any other support staff? If so, how many and what areas of expertise should they have?
User Type A:
Since IWFM simulates many components of the hydrologic cycle as well as the farming and irrigation practices, it generally requires a multi-disciplinary approach, given that most modelers are not experts in all of these fields. Although a user can come up with an initial set of parameters during the calibration phase or the scenario development phase, at some point, it may be required to consult with experts in other fields. For instance, soil scientists can hone the soil parameters while irrigation engineers can perfect the parameters related to farming and irrigation practices. Experts in ArcGIS can develop necessary parameters speedily. Overall, however, if any support staff is required and how many depend on the qualifications and expertise of the individual modeler that is using IWFM.
User Type B:
Similarly, how many support staff, if any, is required depends on the specific scenario a user is trying to put together. A scenario can be as simple as turning off diversions and meeting the demand fully by pumping; such a scenario development requires no support staff. Another scenario can be very complex with new crops using different farming and irrigation schemes coupled with different precipitation and ET requirements. In this case, staff with different expertise can be required depending on the skills of the individual user.
(vii) How much time is needed to assemble the data for each of the models?
This is completely application specific. Utilizing the full capabilities of IWFM – aside from the temporal and scale issues can be data intensive including hydrological, land use, soils, and aquifer parameters and time series. The time required to assemble the data for a 500 square mile basin depends on the complexity of the stratigraphy, farming and irrigation practices (if any), number of crops being planted in the basin, grid resolution, etc. Depending on these factors, data development can take from a few days to several months.
(viii) How much time needs to be spent on calibrating and verifying the model before it is used for predictions?
Similar to item (vii) above, this is application dependent, regardless of the size of the model boundary. Calibration and verification of a model with little or no farming activity, fairly uniform soil and aquifer parameters, and a coarse grid may take a few weeks. A more complex model domain with high heterogeneity in the aquifer and the root zone parameters, many agricultural crops, complex farming and irrigation practices, and fine mesh may require several months for a proper calibration and verification. Use of automated approaches such as PEST greatly facilitate and streamline the process, but at greater cost in technical abilities and computational resources.