MEMORANDUM

To: Members of the Board of Selectmen

From: Jeanne H. Armstrong, President

Date: December 23, 2003

Subject: Findings of Water Budget Analysis required by 418 program

Introduction. Please recall that the scope/contract of for our recently completed Town Center Plan project included the required task of performing a preliminary water budget analysis for Belchertown. The purpose of this analysis is to provide a basis for local communities to consider anticipated development’s long term implications for water demand vs. recharge of underground water supplies. Watershed boundaries ignore political boundaries, so neighboring communities usually share aquifers and subsurface water resources. The water budget effort is intended to prompt sharing of information and policy deliberations about whether and how to coordinate land use management practices to insure needed quantities of underground water for future generations.

The resources of the 418 budget allowed Daylor Consulting Group to use their GIS computer expertise to compare estimated water demand vs. recharge of groundwater at present, with future build out conditions. This preliminary analysis is based upon the current land use map and projected build out map from the build out study performed for Belchertown as part of the state-wide series of buildouts designed and funded by the Executive Office of Environmental Affairs a couple years ago. The results of the analysis are attached.

A word of explanation: One key column in the analysis table is the “% Infiltration” one. At first it seems odd that surface water bodies are assumed to have 0 infiltration, but this is because the entire analysis is focused on determining the proportion of rainwater that percolates down to the water table. Standing water is the water table.

Implications. This very preliminary assessment indicates that Belchertown’s water demand vs. recharge of groundwater will not be out of balance at projected buildout. This is mainly due to so much of Belchertown’s future projected development being single family residential, which has relatively high infiltration of rainwater. Clearly, it will be important to pay close attention over time to minimizing impervious surfaces and maximizing on-site retention of draining water.

Water Budget Analysis for Town of Belchertown

Performed by Daylor Consulting Group

Aim: To determine current water use and recharge potential and compare with future/build-out conditions

Method: To determine the current water recharge potential of Belchertown, the MassGIS 1999 Land Use data was used and compiled into categories as shown below in Table 1 – Belchertown Water Budget Analysis. The description column corresponds to land use codes that were identified by the MassGIS Land Use data. Each land use category was then assigned an impervious cover percentage. These percentages are estimates/averages of typical values that were found in stormwater design manuals and other resources found on the website of the Center for Watershed Protection (www.cwp.org). The impervious cover percentages were then used to determine the percentage of infiltration that would occur on a given land use. The infiltration percentages used in this analysis come from the EPA report on Preliminary Data Summary of Urban Stormwater Best Management Practices. Assuming an annual rainfall of 48.40 inches the recharge volume was then calculated by multiplying the area by the rainfall and %infiltration, for current land use conditions.

The next step was to take the build-out study that was conducted by the EOEA for Belchertown to determine land usage for future conditions. Similarly, recharge volumes for future conditions were calculated by multiplying the area by the rainfall and %infiltraton.

Conclusion: This analysis shows that under current conditions, 62,648 acre-ft of annual recharge occurs on average (or 55.9 million gallons per day); and under the future build-out conditions, the recharge value decreases by approximately 22% and is at 48,752 acre-ft/yr or 43.5 mgd due to the development (mostly residential/single-family) of 22,165.5 acres of currently undeveloped land. Based on the water demand assumption of 75 gallons per person that was used in the EOEA build-out study, the current water demand is estimated at 1.05 mgd and the future water demand at 3.06 mgd. The build-out study also estimated an additional 0.2 mgd for commercial/industrial uses; however, we do not have any data for current conditions to compare both cases.

Table 1: Belchertown Water Budget Analysis
Land Use Category	Description	Area_1999^1 (in acres)	Area_Buildout^2 (in acres)	%Impervious^3	%Infiltration^4	Recharge_1999 (in af/year)	Rechage_1999 (gallons/year)	Recharge Build-Out (in af/year)	Recharge Build-Out (gallons/year)
Single Family	med density	1,006	17,207	40	35	1,420	462,753,564	24,291	7,915,109,910
Single Family (non urban/low density)	low density	3,489	8,851	30	35	4,925	1,604,917,677	12,495	4,071,403,371
Multi Family	multi-family/high density	199	225	80	15	120	39,230,883	136	44,435,382
Commercial	commercial	70	310	80	15	42	13,799,808	188	61,113,436
Office	office		240	80	15	0	0	145	47,313,628
Industrial	industrial	96	192	80	15	58	18,925,451	116	37,811,474
Civic	urban public+cemeteries +powerlines	391	391	50	35	552	179,857,498	552	179,857,498
Park	part rec+urban open+golf	255	255	10	42	432	140,758,042	432	140,758,042
Transportation	transportation	16	16	100	0	0	0	0	0
Undeveloped	crop+pasture+forest+mining+open land+orchard+nursey	27,321	5,156	0	50	55,097	17,953,550,287	10,398	3,388,181,446
Water	water+water based rec	2,511	2,511	100	0	0	0	0	0
Other	waste disposal	48	48	100	0	0	0	0	0
Total		35,402	35,402			62,648	20,413,793,210	48,752	15,885,984,187
Assumptions:
Assume Annual Rainfall - 48.40 inches (Source: USDA - Natural Resources Conservation Service)
1: Area values were calculated using the MassGIS Land Use layer for 1999 for current land use.
2: Future land use breakdown was taken from the EOEA build out study
3: Impervious cover percentages are a compilation of stormwater design criteria manuals, technical papers, and information found in www.cwp.org - Center for Watershed Protection )
4: Source: Preliminary Data Summary of Urban Stormwater Best Management Practices; EPA-821-R-99-012, August 1999, p 4-4