Using GIS in Source Water Assessments

Hampton Roads Source Water Assessment Program

J. Wesley Kleene, Ph.D., P.E., CH2M HILL

Scott Emry, P.G., Hampton Roads Planning District Commission

Linda Warren, P.E., CH2M HILL


Abstract

A comprehensive data management system was developed to support the spatial analysis between potential sources of contamination known as "Land Use Activities (LUAs)" and the drinking water intakes for the eight surface water utility members of the Hampton Roads Planning District Commission (HRPDC). This analysis provided a comprehensive overview of the landuse activities (LUAs) and the landuse patterns within each watershed. The basic approach is defined here with example results to support the Source Water Assessment Reports to be delivered to Virginia Department of Health.

A query-based system was developed and distributed to the stakeholders to support local watershed managers and utilities. The system requirements ultimately included the hardware and software limitations of individual stakeholders and jurisdictions. Therefore, the lowest denominator for delivery was a database (Access) with data linked to GIS layers for viewing in ArcView or ArcExplorer. The logical next phase of the project would migrate the data to an enterprise application using ArcIMS technology.


Introduction

The Hampton Roads Source Water Assessment Program (HRSWAP) was conducted for the Hampton Roads Planning District Commission (HRPDC) Source Water Assessment Program (SWAP) Subcommittee. This cooperation of member local governments established the HRSWAP to promote watershed protection and to fulfill the technical requirements of the Virginia Department of Health (VDH) Source Water Assessment Program (October 15, 1999) for surface water systems and conjunctive use wells. Each utility (or jurisdiction) may contain multiple intakes and associated contributing areas defined as watersheds or buffers surrounding the conjunctive use wells.

Geographic Information Systems and relational database management systems were developed to provide analysis and reporting for the project. In addition to a primary data management tool, these systems were used to provide stakeholders (personnel supporting the water utilities, watersheds, and local jurisdictions) access to the data on a routine basis. Spatial and non-spatial reporting systems were developed to allow the user to query the database, and generate spatial data for viewing or further analysis. Requirements for this system evolved over the life-cycle of the project to include data management (including record updates), generation of spatial files, reports, and data export functions.

Data Management System

A data management and query system was developed to provide the stakeholders and jurisdiction managers access to the landuse activities data. The GIS was used to process the LUAs and associate them with specific watersheds, intakes, well areas, assessment zones, and jurisdictions. The processed data were also stored in the database (along with coordinate data) to allow for query selections and analysis of the potential risk to surface and groundwater. The data management system was an integrated Access application as shown in Figure 1.

Figure 1. HRSWAP Data Management System

Queries to this system result in specific landuse activity data that will support source water assessments, planning and modeling efforts. The basic view for the landuse activities data is presented in Figure 2.

Figure 2. Landuse Activities Information

As noted in the Figure 1 Main Menu, the user can generate a shape file and launch ArcExplorer directly from the Access application. When the shape file is combined with the set of base data layers, the user can readily generate source water assessment maps as shown in Figure 3.

Ultimately, the user can identify areas of interest within ArcExplorer (or other GIS applications) and evaluate the potential impact from the landuse activities within the watershed. The GIS provides a tool for viewing the proximity of landuse activities to other layers such as intakes, roads, and hydrography.

Figure 3. Watershed Map from HRSWAP System

Data Sources and Conversion

Watersheds and assessment areas were delineated on U. S. Geological Survey (USGS) Digital Raster Graphics (DRGs). LUAs were obtained from data sources ranging from federal, state, and local databases to commercially available databases. Local jurisdictions and system stakeholders contributed various levels of data in either electronic or hardcopy format. Once obtained, these data files were clipped to the general study area prior to analysis and processing.

Key coverages developed for this project included watersheds, landuse, LUAs, and intakes (surface and groundwater). General information for these data sources include:

Source Water Assessment Area Delineation

Multiple data sources were combined to generate a comprehensive HRPDC database to link the landuse activities to the water intakes. Spatial data were developed using a variety of methods (digitizing, data file conversion, and spatial modeling). Each jurisdiction (or utility) can contain multiple watersheds and well areas and provided data in different methods/formats.

Once intake locations were obtained and verified, the watersheds of the surface water sources were delineated from USGS Topographic Quadrangle Maps. The boundaries of the watershed were delineated based on topography, hydrology, and transportation information. Where applicable, boundaries of the watershed were delineated by hand until they merged with a boundary already established by the USGS Hydrologic Unit Codes (HUC– 11 digits) or the Virginia Department of Conservation and Recreation (DCR) Hydrologic Sub-Unit Codes (HUC- 14 digits).

The source water zones were defined by the VDH Source Water Assessment Program Guidance (October 15, 1999). For a non-tidally influenced assessment area, Zone 1 is defined as the watershed upgradient of an intake bounded by a 5-mile radius, and Zone 2 is defined as the remaining watershed outside of the 5-mile radius.

The ground water source assessment area, as defined by VDH, is also divided into two zones centered around the groundwater well. Zone 1 is defined as a circle with a 1000 ft fixed radius and Zone 2 is defined as a circle with a 1 mile fixed radius. Additional tools that support travel time calculations from a point source to the well have also been developed, but were not required on this project.

Table 2 summarizes a typical watershed area and source water assessment zones as depicted in Figure 4.

Table 1

Example Source Water Assessment Area Summary

Intake Watershed or Well Assessment Area

Area Zone 1 (acres)

Area Zone 2 (acres)

Total Watershed or Well Assessment Area (acres)

Lake 1

8,628

N/A1

8,628

WB Reservoir

13,612

28,217

41,829

River Watershed

16,231

993,452

1,009,683

Well #1

72

1,939

2,011

Well #4

72

1,939

2,011

1 Note: No part of the intake watershed is greater than five miles from the intake/dam, so there is no Zone 2.

Figure 4. Watershed Zone Delineation

Land Use Classification

Land use classification within the source water assessment areas was obtained from a number of sources. Land use coverages for each jurisdictions were created from a variety of sources. These ranged from Multi-Resolution Land Classification (MRLC) Consortium (Version 05-27-99 with 2000-04 edits), cadastrel mapping, county landuse files, county parcel GIS coverages and associated zoning data. Copies of the land use maps were provided to the local stakeholders for comment. Stakeholder comments were reviewed and incorporated for the development of the final landuse data. Landuse coverages from all the local jurisdictions were evaluated and an attribute mapping methodology created to generate a single HRSWAP landuse coverage. For example, "Residential housing" from jurisdiction A, and "Residential-medium density" from Jurisdiction B were mapped to a single "Residential" attribute in the ultimate HRSWAP landuse coverage.

The GIS was used to generate report summaries of the source water assessment area land use (Example shown in Table 3). These summaries supported a descriptive evaluation of the watersheds for stakeholders and technical staff.

The source MRLC raster data were converted to ARC/INFO GRID format, and then converted to ARC/INFO coverage format. The original NLCD Land Cover Classification System codes were then reclassified according to the uniform land use scheme for HRSWAP, as shown in Table 2. The final data were projected from the original, Albers Conical Equal Area, NAD83, meters, to Virginia State Plane South, NAD83, feet to conform to the project spatial data projection standards.

Table 2

Example of Land Use Summary

Land Use Description

Area Zone 1 (acres)

Area Zone 2 (acres)

Total Watershed Area (acres)

Agriculture: Cropland

1,955

319

2,274

Agriculture: Pasture

2,882

1,968

4,850

Commercial

46

14

60

Forest

3,169

2,804

5,973

Institutional

31

0

31

Light Industrial

11

71

82

Municipal Parks

4

7

11

Single-Family Residential: High Density

84

6

90

Single-Family Residential: Low Density

887

892

1,779

Single-Family Residential: Medium Density

115

0

115

Swamp/Marsh

748

1,881

2,629

Vacant

5

155

160

Water

948

49

997

Total

10,885

8,166

19,051

Table 3

Example of Land Use Conversion Table

HRSWAP Land Use

City A Landuse

City B Landuse

MRLC1

Land Use Codes

Description

Land Use

Land Use Codes

Description

Land Use Codes

Landuse

HR_SFLD

Single-Family Residential – Low Density

21

Low Intensity Residential

HR_SFMD

Single-Family Residential – Medium Density

Single-Family Residential

11

Single-Family or Duplex

HR_SFHD

Single-Family Residential – High Density

High-Density Residential

12

Town House

22

High Intensity Residential

HR_MF

Multi-Family Residential

Multi-Family Residential

13

Multi-Family

HR_OFF

Office

22

Office

HR_COMM

Commercial

Commercial

21

Commercial

HR_LIND

Light Industrial

Industrial

31

Industrial

23

Commercial /Industrial/ Transportation

HR_INST

Institutional

Institutional/ Educational

41

Public/Semipublic

HR_PARK

Municipal Parks

Recreational

54

Park

85

Urban/ Recreational Grasses

HR_HWAY

Roads

61

Street Network

HR_MIL

Military/Federal

42

Military Base

HR_FOR

Forest

57

Forest

41

Deciduous Forest

1. MRLC NLCD Land Cover Classification System Key Rev. July 20, 1999

Ranking and Susceptibility

Once the data layers were combined, the data were used to assess the relative ranking of LUAs within an area, based on the risk of contamination each LUA posed to the water source. The data management system produced reports ranking the landuse activities based on their landuse type, risk to surface or groundwater (based on risks assigned to the landuse type by VDH) and distance to intake. Therefore, within each study area, those LUAs with a "high" surface water risk are ranked based on their linear distance to the intake. While further analysis of this ranking could include more refined distance and potential pathway alternatives, VDH has requested this approach to provide consistent methodologies across statewide studies. Table 4 shows LUAs with a relative ranking and proximity to the intake.

Table 4

Prioritized Ranking of Landuse Activities

HRSWAP ID

LUA Type (1)

SW Risk (2)

Distance to Intake/Well (ft)

Facility Name

Facility Address

18005

Tire Pile

High

2117

Joe's Salvage Yard

1704 Running Road

Gloucester VA 23061

14665

Marina (surface only)

Medium

4547

Beaver Run Park

28687 Roaring Springs Road

Gloucester VA 23061-4248

18809

Truck terminals

Medium

16382

Mobile Home Movers

37022 Old Cabin Lane

Gloucester VA 23061-2825

12359

Agricultural Animal, General

Medium

18314

Bunker Creek Veterinary

7475 Farys Mill Road

Gloucester VA 23061-2924

15030

Construction, Contractor Other

Low

11009

Black’s Chimney Sweep

7239 Farys Mill Road

Gloucester VA 23061-2913

15143

Construction, Contractor Other

Low

11863

Wiley's Roofing Svc

9881 Indian Creek Trail

Gloucester VA 23061-5216

15312

Construction, Contractor Other

Low

17524

Season-All Insulation

19941 Forest Grove Drive

Gloucester VA 23061-2922

20638

Construction, Contractor Other

Low

18888

Anderson Plumbing

12562 Lake View Drive

Gloucester VA 23061-2835

Total LUAs In Each Risk Category:

Low

Medium

High

Zone 1

4

3

1

  1. Sites may be of more than one LUA Type. The LUA Type with the highest associated risk is shown in this table.
  2. SW Risk = Risk to surface water, as defined by VDH (October 15, 1999

Figure 5. Potential Surface Water Risk from LUAs

Conclusions

A well-designed functional data management plan is essential in the development of a source water assessment program. For the HRSWAP, needs of the stakeholders and utilities were assessed prior to the system design and data requirements. The use of GIS and data query tools enhanced the source water assessment. In addition, a data management and query tool was developed and deployed to support a wide range of user technology levels. The system provided users at all levels access to the LUA data, and was linked directly to a spatial display/analysis tool.

The data management platform provided spatial and non-spatial analysis to generate reports, view analytical results, and provide images for data dissemination. The use of GIS provided a unique mechanism to support the stakeholders and the need to disseminate the data to the public at large. Ultimately, this system can be migrated to a platform that will facilitate internet access to the current data management system.


Acknowledgements

The authors wish to acknowledge the following individuals and organizations:

References

Virginia Department of Health's Virginia Source Water Assessment Program Guidelines, Virginia Department of Health, October, 1999 (http://www.vdh.state.va.us/).



Author Information

J. Wesley Kleene, Ph.D., P.E.
Information Solutions Lead
CH2M HILL
13921 Park Center Road, Ste. 600
Herndon, VA 20171
703.471.6405 ext. 4134
703.471.1508 (fax)
wkleene@ch2m.com

Scott Emry, P.G
Project Manager
Hampton Roads Planning District Commission
723 Woodlake Drive
Chesapeake, VA 23320
757.420.8300
757.523.4882 (fax)
semry@hrpdc.org

Linda P. Warren, P.E.
Project Engineer
CH2M HILL
11818 Rock Landing Drive, Ste. 200
Newport News, VA 23606
757.873.1442 ext. 12
757.873.7657 (fax)
lwarren@ch2m.com