WSP08278

• File Number: 8449.926
• Description: South Metro Water Supply Study
• State: CO
• Basin: South Platte
• Date: 2/1/2004
• Author: SMWSS Board
• Title: Technical Appendices - Appendix 3B - Hydrosphere's Model Development Plan
• Water Supply Pro - Doc Type: Publication

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.'101'5414'2' Groundwater Model Development Report

Oct. 11, 2001

Table of Contents

Executive Summary
1.0 Introduction.... .. ..... ....... .. .... ..... I
2.0 SB.74 Model Assumptions and Limitations..... ........ 3
2.1 Stream-Alluvial AquiferlBedrock Aquifer Interactions................. .. ....... 3
2.2 Consideration of Aquifer Interbeds in Regional Groundwater Model.......... 4
3.0 Background.. ....................... ..... .................................5
3.1 Groundwater Model Objectives and Requirements........ ............. .... 5
4.0 Comparative Analysis for Handling Aquifer Interbeds in Regional
Groundwater Model..... ....... ......................... 7
4.1 Regional Groundwater Model Comparative Analysis Approach............. 7
4.1,1 Scenarios Considered............ ........................... ........................... 8
4.1,2 Model Set-up (Boundary and Pumping Conditions) Common
to All Scenarios Investigated .....'''''''' ................. ..........................................8
4.1,3 Base Case (Single Layer) Model Set-up................. .................. ............. .9
4.1.4 Layered Models........................................... ............................... 9
4.1.5 Vertical Conductance Sensitivity Analysis... ................... .... 11
4,2 Results of Comparative Analysis.................. ............ ................. 11
4.2.1 Areal Head ~istributions ....................... ...... ............. .. 12
4.2.2 Well Hydrographs.............................................................. 12
4.2.3 Vertical Head Distributions........................................... ................n. 13
4.3 Summary and Conclusions of Regional Model Comparative Analysis.............14
5.0 Preliminary Review ofS8-74 Groundwater Model................ ................................15
5,1 S8-74 Model Review................................................................................. 15
6.0 Screening of Hydrogeologic Data for South Metro Area. ................................... . 17
6.1 Data Overview and Screening Methodology......... ...................................... 17
6.2 Screening Methodologies ...................................... ..................... .."'''"" ..............18
6.3 Screening Results ................. ................ ................................ ......... ....... .............20
6.3.1 New Data vs SB-74 MDdel Values: Aquifer Tops & BottomB...................21
6.3.2 New Data vs S8-74 Model Values: Hydraulic Conductivity.....................23
6.4 Screening Implications.................. ...... ..... ........... ................. """ ......... .............. ...25
6.4.1 Aquifer Top and Bottom Elevations .........................................................25
6.4.2 Hydraulic Cond uctivity........ ...'" ...... ............ .."" ..... ..... ...... ..................... ...26
7.0 Groundwater Model Development Plan.............................................................c......28
7.1 Incorporating Up-to-date S. Metro Data into Regional Groundwater

model.... ..... ..... ...... ... .... ...... ......... ..... ....... ........ ......... ....... ......... ...... ........... .......... ...29
7.1.i Updating Aquifer Top and Bottom Elevations in Model...........................29
7.1.2 Updating Hydraulic Conductivity Fields in Model...................................30
7.2 Explicitly Addressing Limitations Inherent in S8-74 Approach.......................31
7.3 Local Wen and Well-Field Analysis....................................................................32
7.3,1 Subsurface Hydrologic Processes that Would Increase Local

Drawdowns ... ................... ............ ...... ........ ............... '"'''''''' ......... ....... ...... .33
7.3.2 Recommendation for Local (WeJl and WeJl-Field) Analysis.....................34
7.4 Summary of Model Development Approacb.......................................................35
8.0 BibliograpbL.... ..................................................................................................... .36
Appendix A

Hydrosphere Resource Consultants
1002 Walnut Suilc 200. Boulder, CO 80302
PO Box 44S, Socorro, NM 87801