West Hill Pond Annual Report 2015
by George Knoecklein, PhD
West Hill Pond is the most pristine of all Connecticut lakes with public access. This rank is based on excellent water clarity, low nutrient level, scarcity of aquatic plants, lack of invasive aquatic plants, and well oxygenated waters. It was ranked the 5th cleanest of 70 Connecticut lakes assessed in the 1970’s, and the cleanest of 56 Connecticut lakes in the 1990’s. No assessment of CT lakes has been conducted since that time. Change in rank between 1970’s and 1990’s was due to faster deterioration of lakes ranked higher than West Hill Pond in 1970’s, as each, Bashan, Mashpaug, Highland, and Billings had lower rankings in 1990’s. Details of the 1990’s assessment indicate that West Hill Pond also showed deterioration of water quality in the twenty years between the two studies but at a slower rate than other lakes. Slower decline in water quality could be attributed to West Hill Pond having one of greatest mean depths and one of the smallest watershed to lake area ratios of all Connecticut lakes. This gives the lake a huge advantage because the lake’s massive volume maximizes dilution of the expected low level of nutrient and sediment contributions from the tiny drainage basin.
However, these tremendous assets come with sinister costs that threaten the long-term preservation of the excellent water quality of West Hill Pond.
- The tiny watershed offers no headwater sources of high quality runoff water to mitigate contamination from development along the lakeshore.
- Due to its small size, development can easily expand to cover the entire drainage basin, which could than cause all water entering the lake to be contaminated.
- The lake’s vast water volume will hide slowly deteriorating water quality for a very long time, allowing the lake to appear the same at the surface belying festering problems in its great depths.
- The tiny watershed will cause much of the runoff to pass quickly to the lake with minimal time of contact for remediation. With a large catchment area, tributaries capture large fractions of the runoff and hence allow better recharge and freshening and are representative of significant portions of the landscape. Tributaries of small watersheds drain only small fractions of the land leaving a significant fraction to drain directly to the lake by small uncontrolled drains, surface sheet-flow off lawns and down driveways and private ramps. The small inlets are representative of very small areas of the drainage basin so monitoring results from these small inlets accounts for small areas meaning that fully characterizing the loading from the watershed requires significantly more effort.
- The large volume of the lake makes detecting water quality declines extraordinarily difficult. Because water renewal occurs at such a slow pace it takes many years for true changes to become manifest over the year-year variably caused by climate.
- Once water quality deterioration becomes alarming the massive volume of the lake causes remediation to be extremely difficult to nearly impossible. This will be due to the lake then having an enormous dissolved oxygen debt and internal release of phosphorus over a very large bottom area, extremely degraded water clarity with very high numbers of cyanobacteria and rampant deterioration of drainage basin health leading to fully contaminated ground water.
- a. Remediation of lakes that develop excessive internal loading can only be done
by intensive and expensive means (either whole lake Alum applications or by
whole bottom aeration) causing these lakes to be labeled irretrievable.
- a. Remediation of lakes that develop excessive internal loading can only be done
The findings of this study show that West Hill Pond is at a critical juncture; water quality is still good to excellent but there are indications that conditions are declining. Further deterioration will cause visual changes to begin to be apparent. It is absolutely imperative that exhaustive diagnostic evaluation of lake condition and comprehensive remediation of watershed aliments be accomplished prior to changes in lake quality become noticeable.
Continued development without proper precautions, further disturbance anywhere in the drainage basin but explicitly within 250 feet of shore, lack of attention to impervious surfaces and storm water conveyance, increased human use, and continued disregard for hitchhiking flora and fauna on incoming boats, will greatly accelerate the rate of deterioration of the lake.
Some important early warning signs are;
- increased aquatic plant growth with prevalence of less desirable aquatic plant species along specific reaches of the shoreline,
- increased frequency of filamentous algae and cyanobacteria scums near shore
especially at the outfalls of culverts and inlets streams,
- decreased water clarity in spring or after wet periods,
- decreased summer water clarity,
- increased volume of anoxic water,
- decline of indicator benthic organisms from stream channels,
- and increased quantities of silts and sands at the outfalls of inlets and culverts.
- West Hill Pond, although probably looking similar each year to the untrained eye, is undergoing subtle nutrient loading and declining conditions.
- The lake experienced severe oxygen loss of bottom water that at maximum rendered a large volume of the lake anoxic by October.
- Loss of bottom water dissolved oxygen caused release of phosphorus, ammonia and iron from bottom sediments; with nearly highest levels occurring after the lake had become fully mixed with respect to water temperature.
- Significant amounts of water fully depleted of oxygen at the end of the season indicate that winter oxygen loss could be severe, and phosphorus could be carried over to the next spring.
- Water clarity patterns and higher spring phosphorus levels suggest that nutrient loading during winter months is occurring. No information exists that shows winter of spring inlet nutrient concentrations are increasing.
- Phosphorus concentration in the lake has more than doubled, perhaps tripled, over the last 14 years. Although still relatively low, phosphorus concentration is now at a level where further increases would change the water quality classification of the lake and likely result in additional declines in water clarity.
- Blue-green algae (Cyanobacteria) was found in the water column during the summer and fall months at low levels.
A dense bloom of cyanobacteria with floating scum, was found at the mouth of an inlet at the southeastern corner of the lake during the summer.
- High levels of nitrate and phosphorus in most the drains sampled during the 2015 monitoring year suggests that groundwater to the lake is high in both these nutrients.
- High levels of nutrients in base flows—those sampled during 2015—suggest that storm water nutrient loading could be severe.
- West Hill Pond is extremely vulnerable to nutrient and sediment inputs from its tiny watershed. All current activities in the watershed are impacting the lake to some degree. Current monitoring has not yet determined the magnitudes of impact from each type of land-use, however data collected in 2015 show some inlets had nutrient levels that far exceed permissible amounts.
- Conduct regular and comprehensive lake water quality monitoring.
- Phosphorus levels have inched up to the point where further increases will result in appreciable declines in clarity. The trends of productivity factors discussed in this report require monitoring monthly between ice-out and ice-on with possible over ice sampling conducted in the winter.
- Analysis should be expanded to include additional parameters that enhance and refine our diagnosis of lake condition.
- Continue monitor inlet water quality. Based on results of inlet sampling conducted in 2015, high levels of nutrients are currently entering the lake at several sites.
- Additional eutrophication modeling should be done to better estimate magnitude and sources of loading.
- Expand water quality monitoring to include analysis of storm water as often as possible.
- Eliminate any culverts that directly convey storm water from roads to the lake.
- Inspect all surface drainage ways for erosion.
- Install infiltrating structures wherever possible.
- This survey will identify quantities of phosphorus and nitrate in ground water that enters the lake below the normal summer water level.
- Inspections should include detailed descriptions of at least; type, size, internal integrity, location, water table, soil types in area of leaching fields, presence of wetlands, estimate of distance to lake or nearest water course, approximate percapita use, seasonal vs. year round occupancy.
- State of CT boat should be monitored continuously while open such that no boat accesses the lake without inspection.
- All boats launched from private ramps should be inspected cleared, and tagged by the Lake Association.
- Two annual aquatic plant surveys should be conducted to search for invasive aquatic plant species.
- There are numerous shoreland protection regulations that are in force in other states, Maine and Vermont for example, that can be used as models. Very specific protection is needed now for the shoreline of West Hill Pond that limits future development and further disturbance and sets up a mechanism for gradual return of natural re-vegetated areas that are now disturbed.
- Modify and amend any and all existing regulations to include special lake-specific protection language that accounts for the sensitivity of West Hill Pond.
- All future development, and all existing development, in the drainage basin should be Hydrologically Transparent. West Hill Pond is extremely vulnerable to nutrient and sediment inputs from its tiny watershed.
To read the full report click here.
The West Hill Pond Association has been testing the lake water quality for many , and those reports can be found on the Water Quality Monitoring page.
Since 2006 Dr. George Knoecklein of Northeast Aquatic research has been studying the lake at an increasingly detailed level. In 2015 his focus was on better understanding of the total available phosphorus, the nutrient most impacting lake productivity. What follows is the preface from Dr. George Knoecklein’s report, followed by a link to the entire report.
by Bill Adamsen, Trustee of the West Hill Pond Association