Pollution Prevention - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 452

• Integrate quantity and quality . Reducing stormwater quantity will improve the qual-
ity of receiving waters.
• Recognize the linkages between and within point and nonpoint sources , and optimize
the control measures based on these linkages . Point and nonpoint sources are linked
through surface runoff, groundwater flow, and particulate transport. For example,
using phytoremediation at brownfield sites provides vegetative cover and mini-
mizes erosion and surface runoff.
• Opt for nonstructural (low-cost and nonpermanent) controls first. . Many urban areas
built expensive and permanent combined sewer overflow (CSO) control basins
(e.g., the Rouge watershed) before adequately characterizing the potential of run-
off reduction from nonstructural controls within the watershed (Kaufman and
Marsh 1995).
• Try to maximize the vertical movement of nonpolluted or minimally degraded water . Many
stormwater strategies advocate moving stormwater vertically, but this action can
degrade groundwater and ultimately surface waters if the water is highly contam-
inated. Locations for infiltration should be chosen and prepared carefully so they
have adequate organic content to assist with biodegradation and the adsorption of
organics and heavy metals.
• Pay close attention to erosion control in the headwaters region of the watershed . The high-
est energy gradients are in the first-order stream segments found in the headwaters,
so lowering erosion here lowers the kinetic energy of the stream and minimizes
channel erosion. Reducing the erosion capacity of the streams will reduce the
deposition of materials downstream, and also in the lakes and impoundments
functioning as settling basins.
To support the general objectives above, the following data can be collected and generated:
• Current measures of water quality at several locations throughout the watershed .
Universities and watershed organizations often conduct regular stream sampling
and benthic monitoring, so check with them first. Benthic monitoring collects sam-
ples of materials dislodged from stream beds and assesses the species diversity.
The presence of certain insects, for instance stoneflies, may indicate high water
quality. Remember to also collect samples from wells within the watershed. This
sampling is often free, with collection vials provided by the County Public Health
Department. At a minimum, the parameters tested for in streams and ground-
water should include total suspended solids, pH, dissolved oxygen, temperature,
phosphorus, nitrate, and fecal coliform.
• A stream order map for the watershed . As noted earlier, lower-order streams are more
vulnerable to contamination, so identifying their locations can assist with priori-
tizing source control efforts. Some universities have done this already.
• Hydrographs for all gauged streams within the watershed . A hydrograph is a plot of
discharge ( Q ) over a specified time interval (Figure 13.12). These are available in
different time increments (day, month, and year) from the U.S. Geological Survey.
Hydrographs will help characterize the flood patterns within the watershed. Flood
waters often carry massive amounts of contamination, so knowing where floods
occur more frequently can help direct efforts to minimize stormwater runoff,
which contributes large volumes of water to streams during wet-weather events.