SJRWMD SRWMD Cooperative Groundwater Model Development Project

Transcription

1 SJRWMD SRWMD Cooperative Groundwater Model Development Project Technical Team Meeting December 19, 2012, 9:00 12:00pm St. Johns River Water Management District Headquarters 4049 Reid Street, Palatka, Florida Roll Call 9:30 (computer and telephone issues) Technical Team Members Present: Del Bottcher, Soil and Water Engineering Technology, Inc. (for FFBF, Southeast Milk) Doug Munch SJRWMD, Team Leader Doug Durden - SJRWMD Douglas Dufresne Ardaman & Associates, Inc., (for PCS Phosphate) Fatih Gordu Jones Edmunds (for NFUCG) George Porter JEA, via phone Patrick Burger - SJRWMD Patrick Tara Intera (for SRWMD) Rick Hutton GRU (NFUCG) Jeff Lehnen CH2M Hill, via phone Dale Jenkins - SRWMD Trey Grubbs, SRWMD Peter Schreuder, via phone) Additional participants: Warren Zwanka SJRWMD Andy O Reilly, USGS Meeting Summary The North Florida/ Southeast Georgia groundwater flow model technical team met this day from 10AM to 3:000PM at SJRWMD. Doug Munch welcomed the team and did roll call. The agenda was reviewed. Agenda Item #1 Review October 17, 2012 Meeting Summary The minutes from the October 17, 2012 meeting were made available to the team for review. It was requested the team review the meeting summary and provide comments to Doug Munch by January 4, Agenda Item # 2 Review Action Items from November 9, 2012 meeting

2 1. Discuss with Georgia the model conceptualization relative to including aquifers below the lower Floridan in this model. Doug Durden reported on the teleconference with Jim Kennedy. The result of that conversation is that Georgia is in agreement that aquifers below the lower Floridan need not be included in this model development. Agenda Item # 3 Continuation of the November 9, 2012 meeting discussion a. Rainfall/Runoff/Recharge methodology Del Bottcher provided a PowerPoint presentation on the Water Assessment Model(WMA) that he developed. Del explained there are several methods to consider, NRCS, HSPF, WAM, and SWAT, Green Ampt, EEAMOD a submodel within WAM. Important things to consider are: how good is NRCS, how is the runoff into depressions handled, how is stream, lake, wetland seepage handled. In all of these processes ET should be the reality check. In EAAMOD (Everglades Agricultural Area MOD) or WAM there is a better accounting or representation of in the model of high water table conditions. WAM is essentially a quasi-3d model. It is a public domain model and moderately well documented. It is designed to handle flatwoods conditions with a typical scale of one Hectare, and has a user interface. It has been applied to the entire SR basin (30 yr transient), and in the lower St. Johns River Basin to address agricultural runoff concerns. There are reports and data available for both. The calibration of the model is to surface flows and likely parameter adjustments are usually related to land use or irrigation water source. ET is calculated and imbedded in the model. If this were to be applied in the model domain, it is estimated to take approximately 2 months. The strengths of this model are: flexible to add detail where needed, ability to handle flatwoods, can handle depressions and closed basins, has been used in both SR and SJRwmds. The questions which needs further investigation is the connection or sharing/inputting this model result into MODFLOW. Fatih Gordu provided a PowerPoint presentation on the possible use of HSPF/EPA- Basins. He reiterated the importance of having a good method to formulate recharge and that recharge should not play a large part in the groundwater model calibration. He discussed how HSPF works with EPA basins and data sets can be downloaded from that website to set up the model. Not only can the surface water flows and baseflows be modeled (calculated) in a transient form, it also has an agricultural water estimator package. Following the presentations the team discussed these options for developing a recharge component to the NFSEG model. SR thought both approaches could be used to

3 provide estimates of recharge for the groundwater-flow model. Peter Scheuder posed the question of how good of an estimator could the approaches be. Could a comparison be done? Team agreed that a comparison of models for similar area could be done but time is limited and a decision needs to made on an acceptable approach. Trey Grubbs stressed the need to quantify the uncertainty in the recharge estimates (derived from the rainfall-runoff models) and incorporate this information into the calibration and ultimate use of the model. Three possible approaches were described. The simplest would be to develop the rainfall-runoff model somewhat independently of the groundwater flow model, calibrating the former model using formal parameterestimation methods (e.g. PEST), and using the calibrated recharge rates (and the uncertainty in these rates) from the rainfall-runoff model to constrain the plausible range of recharge rates during the calibration of the groundwater flow model. An extension of this approach would ultimately calibrate both the rainfall-runoff and groundwater flow models simultaneously (e.g. by including them together in the same model-batch file called by PEST), after independent construction of the two models and possibly some initial calibration efforts. This should result in a more robust model calibration (by explicitly including all of the relevant model parameters in the same calibration exercise), and more reliable estimates of the uncertainty of model predictions. The feasibility of this approach will depend on model-run times, however. The most complex option would be a fully integrated gw/sw model similar to that used in the Tampa Bay area, but at the scale of the NFSEG model. However, this approach is beyond the scope of the NFSEG model project. Patrick Tara provided additional information on some of these options and was in agreement with Trey s assessment. The consensus was that the simpler option was probably the best option to pursue at this point. This would allow for employing the simultaneous calibration approach during the model development process. Doug Munch suggested that utilizing HSPF would move SJR toward the long-term plan of developing integrated models; and the District has an experienced staff that utilizes HSPF. There was some discussion on timing and getting the work done. This will be discussed in follow-up meeting with SR. The discussion then moved to the topic of what can be done now to start the initial steady-state calibration exercise. Pat Burger suggested we use what is on the shelf, maybe a combination of SJ HSPF models and SR WAM or evaluate further, what is in the Georgia CDM model. Del Boettcher, Doug Dufresne, and Rick Hutton made comments. The team came to the consensus that HSPF/Basins are the preferable approach to use in the NFSEG model development. Fatih, who brought the item to the technical team, affirmed that he was satisfied with the outcome. Even though there is a consensus on this approach, as the two districts get more involved in the process, it is important that progress or implementation of the approach be reported to the team.

4 Agenda Item # 4 & # 6 Continuation of the original presentation on Model Conceptualization December meeting a. Representation of surface water bodies Surface water bodies are to be represented in the model using the MODFLOW River Package. Hydrograph separation will be used to estimate the baseflow (groundwater discharge) component of total streamflow, which will then be used (along with groundwater levels) to calibrate the groundwater flow model. Fatih is going send the group a USGS reference related to HSPF-calculated baseflow. Patrick Tara gave a brief overview on baseflow calculation and application/representation in the groundwater model. There was some discussion on how intermittent river reaches could or would be handled in the model. For lakes in the model, the technical team decided that maintaining the flux rates is more important than developing a Lake Package for specific lakes given the regional nature of the model. These types of water resource issues can be explored in further sub-regional or local model development. In essence, many of the smaller lakes are an expression of the surficial aquifer system. The Gulf of Mexico will be represented as a GHB and Atlantic Ocean will be represented as a constant head boundary condition expressed in terms of equivalent freshwater head. There was some discussion on the representation of wetlands and the potential for wetlands or ponded water to go dry. There needs to be a more specific description of the approach to wetland representation, such as determining the extent of ponded water and apply bounds in which under a prescribed condition the storage coefficient would change from 1 to a representative value of the surficial aquifer system. There needs to be a determination of the threshold for wetlands to be included in the HSPF model versus ones represented in the groundwater model. b. Sources of initial model parameters The sources for the initial model parameters, to a large extent, will be taken from existing groundwater flow model data sets. There was some discussion on possible approaches for representing hydraulic conductivity values for the surfical aquifer system. These could be derived from soils maps or could be zoned based upon geomorphic provinces. c. Steady-state and Transient Calibration It was discussed that the first round of calibration would be somewhat trial and error for the steady-state calibration. Following the trial and error process, PEST would be

5 applied for refinement in the final calibration of the steady-state and transient models. There was discussion on the calibration criteria and the objectives of the calibration. The group would like to have separate criteria for each individual aquifer. The criteria presented were from the USGS ECFT model. It was discussed these criteria might or might not be the right level of detail based upon the intended purpose of the model. The Team would explore these questions further as the model development progresses. d. Model Capabilities and Limitations Doug Durden generalized the model capabilities and limitations, as reported in the NFSEG Model Conceptualization report. Capabilities include the ability to project drawdown between sub regions and the ability to provide a framework for the development of sub regional groundwater flow models. Limitations include lesser ability to provide detailed, localized assessment of drawdown and limited ability to assess the interaction of groundwater and surface water. The FAS representation within the model will be better than that of the SAS, IAS, or SECPAS. Agenda Item #5 Lunch Agenda Item #6 Continue Model Conceptualization See agenda #4 above for continued discussion Agenda Item #7 Review Action Items 1. Team to review previous meeting summaries and respond to SJRWMD by January Fatih G. to provide links on USGS/HSPF paper to the team. 3. Doug Durden to provide link to Volusia Model for team to review recharge algorithm. 4. Doug Durden to post the PowerPoint s from the presentation for team for future reference. 5. Doug Durden to post the Georgia EPD MODFLOW model report with MODFLOW files. Agenda Item #8 - Public Comment Paul Still commented about the considering the inclusion of Graham Swamp in the proposed USGS sub-regional model. He also commented on internally drained areas in Bradford County and there relation to recharge. He also discussed the significance of Lake Sampson and how the outflow only occurs at or above the 131 foot elevation. Agenda Item #9 Next Meeting

6 The next meeting will be late January or early February. SJRWMD would like to begin discussion on the USGS lake area subregional model and other related items. An will be sent with options for meeting dates for the team to respond. Agenda Item #10 Adjourn meeting