Watershed Management for Potable Water Supply Assessing the New York City Strategy (2000) / Chapter Skim
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2 The New York City Water Supply System
2 The New York City Water Supply System
Pages 45-87
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From page 45... ...
This chapter sketches the historical evolution of the New York City water system in relation to socioeconomic growth of the city during the nineteenth and early twentieth centuries. It then describes the basic physical elements of the system as it exists today, together with the biophysical geography of the CatskilllDelaware headwaters from which 90 percent of the City's water is derived.
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From page 46... ...
The opening of the Erie Canal in 1825, which connected the Hudson River with the Great Lakes, established the City's economic preeminence in the nation and contributed to its rapid population growth and prosperity. Local water sources were hopelessly inadequate to serve this rapid rate of growth in terms of quantity, quality, and pressure.
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From page 47... ...
Damming the Croton River The solution of the New York City water crisis ultimately required a synthesis of innovation in technology, in public administration, and in civic responsibility previously unknown in urban history. These factors, in conjunction with growing public desperation and fear, contributed to a municipal achievement that still today is the envy of other cities worldwide.
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From page 48... ...
A map of the current Croton water supply watershed is given in Figure 2-1. Evolving Public Health Laws During this time, two important public health laws relating to drinking water safety were being developed in New York State that would make continued expansion of the New York City water supply possible.
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From page 49... ...
Courtesy of the NYC DEP.
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From page 50... ...
Between 1907 and 1929, the City acquired water rights and constructed the Schoharie and Ashokan reservoirs in the Catskill Mountains. A new 92-mile Catskill aqueduct conveyed water from Ashokan to the City, crossing under the Hudson River by means of an "inverted siphon" 3,000 It long and 1,100 It below sea level (Weidner, 1974, p.
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From page 51... ...
300~. It meets the Catskill Aqueduct at Kensico Reservoir east of the Hudson River, which it crosses via a deep inverted siphon.
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From page 52... ...
: ::: .. ~ Orange County Atlantic Ocear' 0 20 40 60 80 Kilometers FIGURE 2-3 New York City water supply.
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From page 53... ...
in Great Britain 1825 Erie Canal opened 200,000 1830 1832 Cholera epidemic strikes New York City and other cities 1834 NYC Board of Water Commissioners established by state legislature 1835 Great Fire burns much of New York City 1837 Croton River Dam and 41-mile aqueduct begun 1842 First water reaches New York City from Croton River celebrations 1858 Central Park opened including reservoir 1866 New York State Metropolitan Health Act 1 million 1878 1893 Completion of New Croton River aqueduct 3.5 million 1898 Consolidation of "Greater New York City" five boroughs 1905 State Legislature gives New York City power to regulate upstate watershed land 4.6 million 1911 New Croton River system completed 10 percent of present New York City system 1925 Interstate compact re Delaware River allocation only ratified by New York 1927 Catskill Mountain system completed 40 percent of present New York City system 1931 New Jersey v.
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From page 54... ...
188~. Future Demands on the New York City Water Supply System Average daily demand served by the New York City water supply system declined from 1,547 mad in 1990 to 1,449 mad in 1995 (Hazen and Sawyer/ Camp Dresser & McKee, 1997, p.
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From page 56... ...
Moreover, all three of the identified regions may be expected to experience further population growth over the next two decades which, even without contamination of present sources, may pose the need for at least supplementary augmentation from the New York City system. To the extent that the City' s system is serving a smaller population now than it did three decades ago, it may be viewed by surrounding jurisdictions as a logical source of future water supply.
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From page 57... ...
However, if the issue remains unaddressed, the relevant parties should take whatever steps may be necessary to protect existing user sources against contamination and against rising demand in order to minimize the potential for future demands on the New York City system. DESCRIPTION OF THE NEW YORK CITY WATER SUPPLY SYSTEM The water supply system for New York City is under the jurisdiction of the New York City Department of Environmental Protection (NYC DEP)
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From page 58... ...
Ashokan _ Reservoir ~_ EL. 590.0 - ~West Branch 127.9 B.G.
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From page 59... ...
New York City Drinking Water Reservoirs Croton System The Croton system normally provides approximately 10 percent to 12 percent of the City's daily water supply and can provide up to 25 percent during drought conditions. The system consists of 12 reservoirs and three controlled lakes on the Croton River, its three branches, and three other tributaries (Figure 2-1~.
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From page 60... ...
to Rondout Reservoir, where the Delaware aqueduct begins. Rondout Reservoir drains Rondout Creek, a tributary of the Hudson River; however, most of Rondout's water is from the three upstream reservoirs on the branches of the Delaware River.
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From page 61... ...
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From page 62... ...
Chelsea Pumping Station In times of drought, Hudson River water can be pumped into Shaft 6 of the Delaware Aqueduct from an emergency pumping station at Chelsea. The station was originally constructed in the early 1950s to augment the City water supply prior to completion of the Delaware aqueduct.
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From page 63... ...
Monitoring data from NYC DEP have shown that the water quality at the two Kensico effluent locations (DEL 18 and CATLEFF) is similar, except for slightly higher coliform concentrations at DEL 18 (NYC DEP, 1998~.
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From page 64... ...
64 WATERSHED MANAGEMENT FOR NEW YORK CITY FIGURE 2-6 New York City water tunnels. Courtesy of the NYC DEP.
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From page 65... ...
. Existing Treatment Table 2-3 shows average water quality conditions in the Catskill/Delaware reservoirs from 1992 to 1996.
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From page 66... ...
This section describes the physical attributes of the Catskills, including those that account for New York City' s historically excellent water quality. It then describes the evolving land uses within the region that have influenced the quality of New York City drinking water.
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From page 67... ...
_~ c' - 1 cl cUS04r ma ) Dunwoodb NaOH _ _ _~ 1~ 67 (NO: in Servicer LEGEND Cl- Chlorine F- Fluoride CL`SO4 - Copper sulfate NaOH - Caustic Soda PO4 Orthophosphate By Pass FIGURE 2-7 Potential chemical feed locations for the New York City water supply (not all chemicals and feed locations are used on a regular basis)
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From page 68... ...
From the "High Peaks" area, the plateau tapers to the west into the Delaware Valley and the Finger Lakes region. Catskill Mountains.
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From page 69... ...
{Orographic effects refer to increases in precipitation with increasing elevation as air masses flow up and over mountains. This is common in the Catskill/Delaware region as continental air masses move east from the Ohio Valley or maritime air masses move north up the Hudson River valley.
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From page 70... ...
Therefore, vegetative cover, land use, and resulting pathways and rate of flow play an important role in determining how climatic and hydrologic characteristics affect reservoir water quality. Reservoir Dynamics Water supply reservoirs have many characteristics that are similar to those of natural lakes.
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From page 71... ...
Courtesy of the NYC DEP.
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From page 72... ...
Although most withdrawals are from surface waters, water can be withdrawn from varying depths within all Catskill/Delaware reservoirs except Schoharie Reservoir. The chosen depth of withdrawal depends on turbidity, dissolved oxygen levels, color, and other water quality parameters (Warne, 1999a)
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From page 73... ...
. CFrom 1999 TMDL reports (NYC DEP, l999a-h)
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From page 74... ...
0 6 12 18 Kilometers FIGURE 2-9 General distribution of wetlands and deepwater habitats of greater than 12.4 acres in the Catskill/Delaware watershed. Courtesy of the NYC DEP.
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From page 75... ...
This arbitrarily established size limit is not expected to substantially affect water quality in the reservoirs because wetlands smaller than 12.4 acres in the Catskills do not constitute the more important riparian and headwater wetlands discussed above. Rather, they are isolated depressions on agricultural land in the Cannonsville, Pepacton, and Schoharie watersheds (the second type described above)
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From page 76... ...
Residential and commercial development accounts for a relatively small proportion of watershed land use. However, because this development tends to be concentrated in stream valleys, it can have a disproportionately large influence on water quality.
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From page 77... ...
NYC DEP's "urban" category is a measure of impervious surfaces, major roadways, commercial, industrial, and high- and medium-density residential areas as derived from LAND SAT _ scenes that have a 28.5-m resolution. Source: NYC DEP, 1993b.
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From page 79... ...
Farming and seasonal settlements were clustered in and along floodplains of major streams and along the Hudson River. On a voyage of discovery sponsored by the Dutch East India Company, Hendrick Hudson sails the Half Moon up the "Great River of Mountaynes" [later the North or Mauritius River then, finally, the Hudson River]
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From page 80... ...
1905 New York State Public Health Law authorizes New York City to secure lands, by eminent domain if necessary, to build reservoirs and infrastructure needed to expand the water supply. 1907-1965 Beginning with the Ashokan Reservoir (Esopus Creek)
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From page 81... ...
Population Trends in the Watershed Region One of the reasons the Catskill/Delaware region was tapped for water early in the twentieth century was that it was sparsely populated. There are 40 towns west of the Hudson River with some land in the Catskill/Delaware watershed.
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From page 82... ...
In order to determine actual watershed population figures, the 1990 percentages of the town population residing in the watershed (NYC DEP, 1993b) were used to estimate permanent watershed populations since 1860, with results shown as Curve B in Figure 2-11.
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From page 83... ...
Population growth projections for the Croton watershed are likely to reflect conditions within the Kensico and West Branch watersheds that could have a significant impact on water from the Catskill/ Delaware watershed. The historical and future permanent populations residing in these two basins were analyzed by the same method used for the population residing in the Catskill/ Delaware watershed.
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From page 84... ...
for the New York City watershed regulations projected that in the absence of regulations, the seasonal population would grow at a rapid rate (NYC DEP, 1993b)
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From page 85... ...
This growth in housing in excess of permanent population growth might indicate seasonal home development. One can also evaluate new housing construction rates and approximate corresponding increases in housing stock.
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From page 86... ...
l999h. Proposed Phase II Phosphorus TMDL Calculations for West Branch Reservoir.
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From page 87... ...
1933. Hudson River Landings.
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