These presuppositions led us to define land uses for the web interface based on a blend of existing L-THIA categories and the NIPC "Paint Chip Palette" used in the regional population forecasting process. Commercial and industrial water use varies widely by industry type, but we elected to take an average based on the land use type rather than industry type. As principal investigator, NIPC took the lead in determining the inputs, calculation processes, and outputs of the L-THIA extension, developing a computation flow chart to communicate the results to the project team. NIPC also performed a strategic literature review (still ongoing) to determine the appropriate values to use in the computations. Several GIS studies were undertaken to establish certain land use parameters for the region (e.g., net/gross density by lot size, average landscaped area per residential parcel as a function of lot size, etc.) In addition, NIPC worked with several municipalities to collect water use information to use for benchmarking and verification. NIPC also collected available GIS information from the Illinois State Water Survey for use by Purdue. NIPC also coordinated with the previous project manager, now at Hey and Associates, to determine detention basin volume requirements and leakage rates to estimate the potential contribution of these basins to groundwater recharge.

In January NIPC used the opportunity of its semi-annual Southern Lake Michigan Regional Water Supply Consortium meeting to have a community of experts review the concept and execution of the L-THIA extension. Participants were able to examine a mockup of the website and review the computations behind the interface. We requested that participants fill out a survey form, the results of which indicated that they supported the project on the whole and provided numerous valuable improvements. We are now at the stage of coding the program to run the L-THIA water supply module, and NIPC is working with Purdue to accomplish this. When a beta version is ready (mid-summer), we intend to work with UIC to evaluate the tool in a user group setting.

POTENTIAL APPLICATIONS/BENEFITS
The purpose of this project is to illustrate to local officials with land use control authority the water demand effects of conversion from one land use to another and to relate demand change to expected water availability. As an applied project, the entire point is to influence local government behavior.

KEYWORDS
Water Supply, web-based, land use change, water resources, development

LAY SUMMARY
Raising awareness among local decision-makers in northeastern Illinois about the effects of land use on water supply remains crucially important. In addition to the high ranking this issue received the Northeastern Illinois Planning Commission’s (NIPC) Strategic Plan for Water Resource Management published in 2001, concern remained strong throughout NIPC’s larger Common Ground planning process, which ended last year and resulted in the 2040 Framework Plan. This plan calls for improved awareness of water quantity issues in the region and stepped-up efforts to plan for the judicious use of available water supplies. The current project attempts to illustrate to local officials, NIPC’s primary constituency, the water resource consequences of land use decisions by giving them a web-based model that calculates the expected change in water demand with development and relates it to expected availability. To do so we are collaborating with Purdue University to build an extension into the existing Long-Term Hydrologic Impact Assessment (L-THIA) model available online. L-THIA now computes expected stormwater runoff and pollutant loadings given land use scenarios provided through user input. The current project will add a water quantity module to complement the water quality focus of the core L-THIA model, allowing local government users to determine whether their decisions are expected to be sustainable with regard to water supplies and providing them options for reducing their “hydrologic footprint.”

PARTNERSHIPS WITH OTHER INSTITUTIONS/INDIVIDUALS INITIATED OR CONTINUED BY YOUR PROJECT
Purdue University, University of Illinois at Chicago

UNDERGRADUATE/GRADUATE NAMES AND DEGREES
None; however, Purdue's part of the project includes support for a graduate student, and UIC may partly support a graduate student in the upcoming months.