Getting Our Feet Wet in the Sheldrake River
Westchester County has many rivers, lakes and reservoirs, which support various needs such as drinking water for both Westchester and NYC, recreation and wildlife habitat. A variety of factors can cause water quality to deteriorate; a primarily cause is the impact of human activities such as the use of excessive pesticides, herbicides and other chemicals. To protect these valuable resources, the County instituted a program of water quality monitoring to be able to observe the possible human or other impacts on water quality.
In 2003 the County created the Westchester County Citizen's Volunteer Monitoring Program or WCCVMP. The program is funded through the Safe Drinking Water Act distributed by the New York State Department of Environmental Conservation. The program was established to collect baseline water quality data on both lotic (streams and rivers) and lentic (ponds and lakes) waterbodies for watersheds of Westchester County and to make this water quality history accessible to the public.
This program continued in 2004, and more citizen volunteers were recruited. All volunteers participated in a three-part training workshop held in Spring 2004, to learn water quality collection procedures. Volunteers joined a monitoring team and each team was assigned a location on a particular stream in the County to be monitored. One of these teams is the Sheldrake Team, which monitors the water quality of the Sheldrake River at Columbus Park in Mamaroneck.
To achieve a complete understanding of the water quality changes over time, the physical, chemical and biological characteristics of the sampling sites are assessed. The specific parameters being tested are listed below.
Physical
Chemical
Biological
Flow
Alkalinity
Macroinvertebrates
Turbidity
Chloride
(water critters)
Substrate
Conductivity
Water Appearance
Dissolved Oxygen
Stream Banks and Channel
Nitrate-Nitrogen
Stream Habitat
pH
Riparian Zone
Phosphate
The monitoring report for 2003 is available to the public at the Westchester County website. According to this report Sheldrake River drains approximately 6.1 square miles with average stream width of 9 meters into the Mamaroneck River. The River is located in a suburban residential area with fair vegetative coverage and good bank stability and preservation.
There are two types of monitoring frequencies that need to be carried out by the volunteers. The first is a weekly monitoring and the other is biannually. The weekly monitoring covers data that changes rapidly such as chemical and certain physical characteristics, while data that does not change so rapidly, such as the substrate conditions, conditions of the stream banks and the presence of macroinvertebrates, are collected two times a year, once in the Spring and again in the Fall.
The 2004 Sheldrake Team began its monitoring session April 25th and ended September 24, 2004. Each data collection session would take between two to three hours. Ideally each team should collect samples and measurements weekly, but this was not always possible. A number of scheduled sessions were cancelled due to whether conditions.
Preliminary observations from the 2004 Sheldrake River data indicate that overall the water quality is good. Most of the measurements are within the specified ranges. The river flow is between 0.2 to 1.1 m3/sec and temperature ranged from 17o to 23.3o C. The River has rather high phosphorus levels, which at times were above the recommended values, while the pH level is between 7.4 and 8.23, which meets the NY Standard between 6.5 and 8.5.
Conductivity is measured in micromhos per centimeter (µhos/cm) or microsiemens per centimeter (µs/cm). Studies of inland fresh waters indicate that streams supporting good mixed fisheries have a range between 150 and 500 µhos/cm. Conductivity outside this range could indicate that the water is not suitable for certain species of fish or macroinvertebrates. The measurements of the Sheldrake ranged from 272 to 655µhos/cm with an average 365µhos/cm. While at times conductivity exceeded the recommended level, on the average it is acceptable.
Some of the pollution sources include fertilizer applied to agricultural fields, timbered areas, golf courses, gardens and lawns. The most common chemicals in fertilizer are nitrates and phosphates. NY law requires that the amount of nutrients not “result in the growth of algae, weeds, and slimes that will impair uses”. It is recommended that nitrate levels remain below 10 mg/l; the nitrate levels in Sheldrake ranged from 0.3 – 1.6 mg/l. The recommended phosphate levels should be below 0.1 mg/l. The measurements at Sheldrake ranged from 0.19 – 0.81 mg/l with an average of 0.44, which is considerably above the recommended level.
In the end, the Sheldrake team completed 11 monitoring sessions including two biannual measurements. The data have been uploaded to the Westchester County’s website and the public can observe them through www.westchestergov.com/cvmp.
Sam Suharto