Hydrologic Assessment Executive Summary
Excerpted from the Hydrologic Assessment study, March 2002.

ES.1 Introduction
In 1994, Massachusetts embarked on a new approach to environmental management -
the Watershed Initiative. Because the initiative involves the state's coordination of its
decision-making process across regulatory programs, the multi-disciplinary Basin
Teams were created with the goal of understanding watersheds and the impacts of
decisions from various regulatory programs. This study was prepared for and
funded by the Massachusetts Executive Office of Environmental Affairs on behalf of
the Nashua River Watershed Team in response to DEM RFR #450, as part of the
Massachusetts Watershed Initiative. The work was completed by Camp Dresser Mckee
(CDM) in June 2002.

Available water is a critical component for the future of Nashua River watershed
residents and for protection of aquatic resources. Despite being in a water-rich
region, many rivers in Massachusetts are severely flow stressed. This project provides
the foundation on which future water use decisions can be made in the Nashua River
watershed.

The relationship of water withdrawal and wastewater discharge and their effect on
river flow is the main objective of this study. In addition, this report examines the
effects of future population growth and the associated demand for additional water
supply sources and increase in wastewater flow.

The tasks set forth in this report are similar to the river basin plans historically
produced by DEM in conjunction with other state and regional planning agencies.
The findings of this report are intended to be used as a basis for water management
and wastewater discharge permitting and to assess the potential impacts to biological
resources of the watershed that may result from consumptive uses of water.

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ES.2 Watershed Description
The Nashua River watershed is 538 square miles in area and contains all or part of 31
communities. Seven of the communities are in New Hampshire and the remaining 24
communities are in Massachusetts. Figure ES-1 presents the Nashua River watershed.
The communities include older, urbanized cities such as Leominster and Fitchburg
and smaller, rural towns such as Ashby and Princeton. The population of many of the
towns in the watershed is increasing rapidly, with some having growth rates of 20%
predicted over the next twenty years. Flows associated with Devens are accounted
for in the flows of the four local communities that make up Devens.

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ES.3 Water Supplies
The headwaters of the Nashua River contain Wachusett Reservoir, a major water
supply for the metropolitan Boston area. In addition, the City of Worcester has
several reservoirs in the headwaters of the Nashua River, which that city uses as
water supply. Nineteen communities in the watershed withdraw water either from
groundwater wells or from surface water reservoirs for public water supplies. Future growth in these communities will put greater demand on the water resources in the Nashua River.

The existing water suppliers withdraw 183 mgd annually from the groundwater and
surface waters in the watershed, or 25.7 mgd if Worcester's and MWRA's water
supplies are excluded. The water need for communities with supplies in the
watershed is forecasted to increase to 187 mgd in the year 2020 or 29.7 mgd if
Worcester and MWRA water supplies are not included.

Currently, 23.8 mgd of water is distributed in water service areas annually in the
basin by the public water suppliers. This amount is forecasted to increase to 28.3 mgd
in the year 2020.

The assessment of water conservation by the public water suppliers found room for
improvement. Two metrics, residential water use of 80 gpcd or less and unaccounted
for water (UAW) of 15 percent or less, were used to evaluate the water conservation
programs for each public water supplier. Five out of 25 water suppliers exceeded the
residential benchmark of 80 gpcd. Eight water suppliers exceeded the UAW
benchmark of 15%. In most cases, the water supplier explained the high UAW in the
Annual Statistical Report (ASR) submitted to the Department of Environmental
Protection. Additionally, seven public water suppliers reported UAW 5% or less,
which is unlikely to be accurate.

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ES.4 Water Supplies at Risk
An evaluation was performed to identify public water supplies that are in proximity
to either a Massachusetts Contingency Plan (MCP) site or solid waste facility. A
ranking system was developed based on the proximity and the risk posed by the site
to the water supply. Six community water supplies and three non-community water
supplies were considered to be at risk from either a nearby MCP site or a solid waste
facility.

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ES.5 Wastewater Discharges
Seventeen communities have wastewater collection systems in the watershed. A total
of 25.0 mgd of wastewater is collected annually in the watershed. The amount of
wastewater collected is forecasted to increase to 32.7 mgd in the year 2020. Currently,
four communities export wastewater from the watershed: Ashburnham and Gardner
(to Gardner's Wastewater Treatment Plant in the Millers River watershed), and West
Boylston, Holden and Rutland (to Worcester's Upper Blackstone wastewater
treatment plant).

The Nashua River and its tributaries receive the discharge of wastewater from seven
public wastewater treatment plants. Three wastewater treatment plants discharge to
the North Nashua River. Wastewater treatment plants also discharge to the main
stem of the Nashua River.

The North Nashua River is a good example of the impact of water withdrawal and
wastewater discharge. The headwaters of the North Nashua River contain numerous
water supply sources, both groundwater and surface water reservoirs. Water is
withdrawn from these headwater sources and discharged downstream at the
municipal-owned wastewater treatment plants of Fitchburg and Leominster.

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ES.6 Inflow/Outflow Analysis
An inflow/outflow analysis for the Nashua River was performed. The watershed
was divided into 27 separate subareas, which were used to calculate the water balance
at a small scale. This process was performed to determine areas of the watershed that
may be subject to diminished river flow, as well as areas that may have the potential
for additional withdrawal. The 27 subareas have been grouped into five separate
subwatersheds: the Wachusett, North Nashua River, Squannacook River, Nissitissit
River, and main Nashua River.

The approach used in the inflow/outflow analysis was to tally the sources and uses of
water in each subarea. Information was collected on the location of water supply
withdrawals, water distribution and wastewater collection service areas, and areas
where wastewater discharge. Annual, August, and winter demand periods were
evaluated.

Annual 2000
The 2000 annual inflow/outflow analysis shows a net gain of 0.7 mgd for the
Nashua River watershed or a net loss of 156.5 mgd when MWRA's and Worcester's
water withdrawals are included.

The findings for individual subareas in the watershed are more telling. Of the 27
subareas in the watershed, only eight have a net gain of flow, and 19 subareas have
a net loss of flow. Of the eight subareas that gain flow, five of these subareas gain
flow from having a wastewater treatment plant discharge in the subarea.

August 2000
For this scenario, there is a net loss of 1.1 mgd for the Nashua River watershed or a
net loss of 165.9 mgd if MWRA's and Worcester's withdrawals are included.
Water withdrawn in August (29.8 mgd) is 3.5 mgd greater than the average annual
volume (26.3 mgd), primarily to meet the greater summer water demand.
Of the 27 subareas in the watershed, 9 have a net gain of water and 18 have a loss of
water.

Annual 2020
For this scenario, there is a net gain of 0.3 mgd for the Nashua River watershed or a
net loss of 157.2 mgd if MWRA's and Worcester's withdrawals are included.
Water withdrawn (30.0 mgd) predicted in 2020 will increase by 3.7 mgd over the
annual amount withdrawn (26.3 mgd) in 2000 primarily to meet the increase in
water demand.

Wastewater collection is forecast to increase from 25.0 mgd in 2000 to 29.9 mgd in
2020, an increase of 4.9 mgd.

Of the 27 subareas in the watershed, 9 have a net gain of water and 18 have a loss of
water.

August 2020
For this scenario, there is a net loss of 1.9 mgd for the Nashua River watershed or a
net loss of 167.4 mgd if MWRA's and Worcester's withdrawals are included.
Water withdrawals (34.3 mgd) predicted in 2020 will increase by 4.5 mgd over the
August 2000 withdrawn amount withdrawn (29.8 mgd) in 2000, primarily to meet
the increase in water demand.

Wastewater collection is expected to increase from 20.3 mgd in 2000 to 24.7 mgd in
2020, an increase of 4.4 mgd.

Of the 27 subareas in the watershed, 9 have a net gain of water and 18 have a loss of
water.

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ES.7 Subarea Flow and Stream Flow
The average August and 7Q10 flows, for existing and future scenarios, were
compared with predicted virgin flows in order to approximate the level of stress of
each subbasin. DEM guidelines, as described in the draft memorandum: Stressed
Basins in Massachusetts (Office of Water Resources, February 26, 2001) were followed
to estimate the stress level of each subbasin.

The DEM has defined three hydrologic stress classifications:

• High-Stress: net outflow equals or exceeds estimated natural August median flow
• Medium-Stress: net outflow equals or exceeds estimated natural 7Q10 flow
• Low-Stress: no net loss to the sub-basin.

Based on these classifications, the stress levels for each subarea were determined for
existing conditions (year 2000) as well as predicted conditions in the year 2020.

Following the DEM stress classification system
One subarea-Flag Brook-is predicted to be highly stressed (net withdrawals
exceeding median August flow) in the Nashua River Basin under either existing
condition. Additionally, Monoosnoc Brook is predicted to be highly stressed in the
future (2020).

Seven subareas are predicted to have medium stress under existing conditions (net
outflow equal/exceeding natural 7Q10): Quinapoxet River 2, Wachusett Reservoir,
Monoosnoc Brook, Falulah Brook, Fall Brook, Wekepeke Brook, and Mulpus Brook.
In the future (2020), Quinapoxet River 1 and Catacunemaug Brook are expected to
be added to the medium stress list.

It is important to note that a large number of the subareas predicted to have some
form of stress also contain multi-month reservoirs. These reservoirs are capable of
storing large flows in the spring and holding them for use during low flow periods in
late summer. Because of the stored volume, the impact of large demands in these
basins may not be as great as the stress-classification system implies; it is possible that
normal low flows are still being released from these reservoirs. To properly determine the stress levels in these basins, a more detailed study of each subarea is
required.

Because the Wachusett watershed is highly managed for the Worcester and MWRA
withdrawals, these withdrawals were not considered in the evaluation of stress in the
Wachusett Watershed-a much more detailed analysis would be required to evaluate
their uses. Instead, the calculations were based on other uses of water in the
watershed, particularly withdrawals by Holden, Rutland, Princeton, Sterling, and
West Boylston. Based on these withdrawals, three of the four subareas in the
Wachusett Watershed were calculated to have medium-stress in the future.
This definition of stress is for water supply purposes. Stress can also be induced on
aquatic life from poor water quality, loss of habitat, and for flow reductions less than
those defined above.

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ES.8 Recommendations
The findings indicate that 11 of the 27 subareas in the Nashua River watershed are or
will be either high stressed or medium stressed under the DEM classification system.
The stressed subareas are predominately in the Wachusett and North Nashua
subwatersheds. The following is recommended for the stressed subareas:

• More detailed inflow/outflow analysis to assess the water balance of the multi-month reservoirs.
• Critical review of any additional water supplies that may be sought in the stressed subareas.
• Emphasis on development and implementation of water conservation plans for communities with supplies in the stressed subareas, especially for those
  communities that do not meet the benchmark levels.
• Assessment of aquatic habitat impacts from worsening flow stresses.
• Critical review of any additional sewering in the basin, especially sewering that moves water out of a stressed subarea or out of the basin.
• Wastewater reuse or artificial recharge of wastewater discharges should be
  considered for any WWTP expansion in stressed subareas.

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Additional detail for most impacted sub-basins

Quinapoxet River (upper reaches - from the Quinapoxet Reservoir up)
Based on recent findings in an Hydrologic Analysis (inflow/outflow) by Camp, Dresser, Mckee, under contract with EOEA for the Massachusetts Watershed Initiative Nashua Team, the Quinapoxet sub-basin is currently under a medium level of stress. With continued withdrawals over the next 20 years, the entire Quinapoxet sub-basin will be experiencing flow stress. The upper reaches as defined above will remain under "medium stress". The lower reaches (remaining portion discharging directly to Wachusett reservoir) will also be under medium stress.

Medium stress means that the net 7Q10 outflow from the sub-basin equals or exceeds the estimated natural 7Q10. 7Q10 is the lowest consecutive 7 day streamflow that is likely to occur in a ten year period in a particular river segment.

High stress means that the net average August outflow from the sub-basin equals or exceeds the estimated natural August average flow.

For the Upper Quinapoxet:
The calculated 7Q10 virgin flow (estimated undeveloped or pre-development) is 0.275 MGD (million gallons/day) and the existing 7Q10 is (- 0.718 MGD). In other words — if the Quinapoxet had never been developed 0.275 MGD should be passing through during a seven day — 10 year low. However, the real seven day — 10 year low is (- 0.718 MGD) — meaning it would be drawing from the aquifer for the discharge.

The calculated average August virgin flow 3.460 MGD and the existing average August flow is 2.467 MGD — a deficit of about 29%

The calculated 2020 average August virgin flow remains the same 3.460 MGD and the 2020 average August flow is 2.078 MGD — a deficit of about 40%

For the Lower Quinapoxet (below the Quinapoxet Reservoir): which is currently considered under "low stress"
The calculated 7Q10 virgin flow (estimated undeveloped or pre-development) is 0.567 MGD (million gallons/day) and the existing 7Q10 is 0.188 MGD. In other words — if the Quinapoxet had never been developed 0.567 MGD should be passing through during a seven day — 10 year low. However, the real seven day — 10 year low is 0.188 MGD.

The calculated average August virgin flow 7.123 MGD and the existing average August flow is 6.744 MGD — a deficit of about 5%.

The calculated 2020 average August virgin flow remains the same 7.123 MGD and the 2020 average August flow is 6.230 MGD — a deficit of about 15%. Putting the lower Quinapoxet into a category of "medium stress"

Wachusett Reservoir (see above note about reservoir operations)
Based on recent findings in an Hydrologic Analysis (inflow/outflow) by Camp, Dresser, Mckee, under contract with EOEA for the Massachusetts Watershed Initiative Nashua Team, the Wachusett sub-basin is currently under a medium level of stress. With continued development and withdrawal pressures, the sub-basin will continue as "medium stress" by the year 2020. It should be noted that while there is a minimum flow requirement for discharge over the Wachusett Dam, local and regional water suppliers need to recognize the importance of continuing demand for supply on the reservoir

This means that the net 7Q10 outflow from the sub-basin equals or exceeds the estimated natural 7Q10. 7Q10 is the lowest consecutive 7 day streamflow that is likely to occur in a ten year period in a particular river segment.

The calculated 7Q10 virgin flow (estimated undeveloped or pre-development) is 0.357 MGD (million gallons/day) and the existing 7Q10 is 1.824 MGD. In other words — if the Wachusett had never been developed 0.357 MGD should be passing through during a seven day — 10 year low. However, the real seven day — 10 year low is 1.824 MGD. Note, the Massachusetts Water Resources Authority is required to maintain a minimum release of about 1.8 MGD over the Wachusett Dam.

The calculated average August virgin flow 4.485 MGD and the existing average August flow is 2.181 MGD — a deficit of about 51%.

The calculated 2020 average August virgin flow remains the same 4.485 MGD and the 2020 average August flow is 1.621 MGD — a deficit of about 64%.

Flag Brook (see above note about reservoir operations)
Based on recent findings in an Hydrologic Analysis (inflow/outflow) by Camp, Dresser, Mckee, under contract with EOEA for the Massachusetts Watershed Initiative Nashua Team, the Flag Brook sub-basin is currently under a high level of stress, and will continue a high level of stress into 2020.

This means that the net average August outflow from the sub-basin equals or exceeds the estimated natural August average flow.

The calculated 7Q10 virgin flow (estimated undeveloped or pre-development) is 0.689 MGD (million gallons/day) and the existing 7Q10 is (-3.935) MGD. In other words — if Flag Brook had never been developed 0.689 MGD should be passing through during a seven day — 10 year low. However, the real seven day — 10 year low is (-3.935) MGD — meaning it would be drawing from the reservoirs and aquifer for the discharge.

The calculated average August virgin flow 4.255 MGD and the existing average August flow is (-0.369) MGD — a deficit of over 109%.

The calculated 2020 average August virgin flow remains the same 4.255 MGD and the 2020 average August flow is (-0.818) MGD — a deficit of over 120%.

Monoosnoc Brook
Based on recent findings in an Hydrologic Analysis (inflow/outflow) by Camp, Dresser, Mckee, under contract with EOEA for the Massachusetts Watershed Initiative Nashua Team, the Monoosnoc sub-basin is currently under a medium level of stress, but it is bordering on a high level of stress. Looking ahead to the year 2020, the Monoosnoc is placed under a high level of stress.

This means that the net 7Q10 outflow from the sub-basin equals or exceeds the estimated natural 7Q10. 7Q10 is the lowest consecutive 7 day streamflow that is likely to occur in a ten year period in a particular river segment under current conditions.

And in the 2020 projection for a high stress level, the net average August outflow from the sub-basin equals or exceeds the estimated natural August average flow.

The calculated 7Q10 virgin flow (estimated undeveloped or pre-development) is 0.622 MGD (million gallons/day) and the existing 7Q10 is (-2.519) MGD. In other words — if the Monoosnoc had never been developed 0.622 MGD should be passing through during a seven day — 10 year low. However, the real seven day — 10 year low is (-2.519) MGD - meaning it would be drawing from the aquifer for the discharge.

The calculated average August virgin flow 3.840 MGD and the existing average August flow is 0.699 MGD — a deficit of about 82%.

The calculated 2020 average August virgin flow remains the same 3.840 MGD and the 2020 average August flow is (-0.194) MGD — a deficit of over 100%

Fall Brook
Based on recent findings in an Hydrologic Analysis (inflow/outflow) by Camp, Dresser, Mckee, under contract with EOEA for the Massachusetts Watershed Initiative Nashua Team, the Fall Brook sub-basin is currently under a medium level of stress. Looking ahead to the year 2020, Fall Brook remains under a medium level of stress.

This means that the net 7Q10 outflow from the sub-basin equals or exceeds the estimated natural 7Q10. 7Q10 is the lowest consecutive 7 day streamflow that is likely to occur in a ten year period in a particular river segment.

The calculated 7Q10 virgin flow (estimated undeveloped or pre-development) is 0.393 MGD (million gallons/day) and the existing 7Q10 is (-0.277) MGD. In other words — if Fall Brook had never been developed 0.393 MGD should be passing through during a seven day — 10 year low. However, the real seven day — 10 year low is (-0.277) MGD — meaning it would be drawing from the aquifer for the discharge.

The calculated average August virgin flow 2.426 MGD and the existing average August flow is 1.756 MGD — a deficit of about 28 %.

The calculated 2020 average August virgin flow remains the same 2.426 MGD and the 2020 average August flow is 1.573 MGD — a deficit of about 35%

Wekepeke Brook
Based on recent findings in an Hydrologic Analysis (inflow/outflow) by Camp, Dresser, Mckee, under contract with EOEA for the Massachusetts Watershed Initiative Nashua Team, the Wekepeke sub-basin is currently under a medium level of stress. Looking ahead to the year 2020, Wekepeke Brook remains under a medium level of stress.

This means that the net 7Q10 outflow from the sub-basin equals or exceeds the estimated natural 7Q10. 7Q10 is the lowest consecutive 7 day streamflow that is likely to occur in a ten year period in a particular river segment.

The calculated 7Q10 virgin flow (estimated undeveloped or pre-development) is 0.125 MGD (million gallons/day) and the existing 7Q10 is (- 0.712) MGD. In other words - if the Wekepeke had never been developed 0.125 MGD should be passing through during a seven day — 10 year low. However, the real seven day — 10 year low is (- 0.712) MGD — meaning it would be drawing from the aquifer for the discharge.

The calculated average August virgin flow 5.254 MGD and the existing average August flow is 4.416 MGD — a deficit of about 15%.

The calculated 2020 average August virgin flow remains the same 5.254 MGD and the 2020 average August flow is 4.211 MGD — a deficit of about 20%

Mulpus Brook
Based on recent findings in an Hydrologic Analysis (inflow/outflow) by Camp, Dresser, Mckee, under contract with EOEA for the Massachusetts Watershed Initiative Nashua Team, the Mulpus Brook sub-basin is currently under a medium level of stress. Looking ahead to 2020, the Mulpus remains under a medium level of stress.

This means that the net 7Q10 outflow from the sub-basin equals or exceeds the estimated natural 7Q10. 7Q10 is the lowest consecutive 7 day streamflow that is likely to occur in a ten year period in a particular river segment.

The calculated 7Q10 virgin flow (estimated undeveloped or pre-development) is 0.173 MGD (million gallons/day) and the existing 7Q10 is (-0.396) MGD. In other words - if Mulpus Brook had never been developed 0.173 MGD should be passing through during a seven day — 10 year low. However, the real seven day — 10 year low is (-0.396) MGD - meaning it would be drawing from the aquifer for the discharge.

The calculated average August virgin flow 7.233 MGD and the existing average August flow is 6.665 MGD — a deficit of about 7.8%.

The calculated 2020 average August virgin flow remains the same 7.233 MGD and the 2020 average August flow is 6.646 MGD — a deficit of about 8.1%.

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Tables
Existing (2000) Stress Level
Predicted (2020) Stress Level

Maps:
August (2000) Water Balance
August (2020) Water Balance