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LAND USE EFFECTS ON THE HYDROLOGICAL CYCLE
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1. Vapor condenses to form rain or snow.
2. Evaporation increases the concentration of minerals left on earth.
3. Water quality of lakes changes due to physical, chemical and biological
processes. The quality of surface water is modified by contact with soil and air. Irrigation increases the concentration of salts in the water. Surface
water quality is further modified by chemical reaction among salts, sediments and biological materials in the water.
4. Cities and factories Water vapor mixes with gas and dust clouds.
5. add chemical and organic pollutants to the water
6. Groundwater is
modified chemically and physically by minerals and gases dissolved from rocks. There is also mixing along the salt and fresh water interface.
7.
Salt water from the ocean mixes with fresh water from rivers (surface water). Water quality in the ocean is also altered by physical, chemical and
biological processes.
8.Dust and spray are picked up by air movements from land and/or water sufaces and introduced into the atmosphere.
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Source: H.A. Swanson and H.L Baldwin, A Primer on Water Quality
(Washington, D.C.: U.S. Geological Survey, 1965).
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Water that enters streams and rivers from urban areas is often routed through a storm-water drainage
system that collects rainwater. These systems are usually separate from wastewater treatment systems. Typically, rainfall picks up contaminants like oil and grease from
roads, herbicides and pesticides from lawns and gardens, and household chemicals improperly disposed of by residents.Under the NPDES (National Pollution Discharge Elimination System)
permit, large cities and construction companies are required to treat storm water and develop management techniques to address these pollution sources.
Stormwater Permits
Municipal and industrial wastewater permits may include requirements to regulate the discharge of storm-water
runoff based upon site-specific circumstances. In 1991, for example, 439 of 966 state discharge permits regulated storm-water discharges from industry.* Since then, virtually all industiral discharge permits regulate storm-water discharges either through an
individual permit, a "general" permit where certain requirements are met, or in some cases, through municipal stormwater permits which incorporate the industrial outfalls.
Until the federal government delegated to Texas responsibility for the discharge permit program in 1998 to the TNRCC
-- now called the TCEQ -- storm-water disharge permits were issued by the EPA. The 1987 amendments to the Clean
Water Act required that storm-water discharges be permitted in two phases. Phase 1 required all pre-1987 dischargers
as well as industries, construction projects covering more than five acres, and cities over 100,000 population with a
separate storm-water sewer system to obtain an "NPDES" permit. Currently, there are 22 cities in Texas, including
some unincorporated portions of Harris County, that have obtained or in the process of obtaining Phase I storm-water discharge permits.* In 1999, the EPA issued final regulations for Phase II, which covers municipalities with more than
10,000 but less than 100,000 population, as well as construction activities which disturb more than one acre of land.
However, some municipalities will have up to six years to apply for a permit, and only those Phase II dischargers
considered to be significant sources of pollution to water quality will be required to seek a full-blown permit. In
addition, the TCEQ has issued a "general" stormwater permit which some smaller municipalities may qualify for, so that
an individual permit would not be needed. Supplemental Phase II rules have also been developed to offer flexibility in the permitting process.
Construction, Pollution, and Impervious Cover
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FYI
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The EPA estimates that each American household generates twenty pounds of
home-chemical waste each year, much of which is improperly disposed of and ends up in rivers, lakes, and aquifers. In an effort to control this non-point-source
pollution, many communities have set up home-chemical waste programs to encourage proper disposal of household chemicals. In Texas, such programs are voluntary.
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Construction, especially that associated with highway building, can also be a major
source of sediment and other non-point-source pollution. The Texas Department of Transportation requires contractors to meet standards for mitigation of construction
runoff during roadwork, but many environmentalists consider these standards inadequate. They argue that construction and development inevitably increase
impervious cover, which prevents rain from being absorbed into the ground and thereby increases runoff that can contaminate streams and rivers.
Previously, under Section 26.177 of the Texas Water Code, all Texas cities with a
population above 5,000 had to submit a pollution abatement plan to the TNRCC. These abatement plans must address both storm-sewer discharges and urban runoff.* However, in 1997 the legislature loosened this requirement to apply only to
cities with populations greater than 10,000 and only to those cities where either TNRCC or Clean Rivers Program assessments had demonstrated pollution impacts from nonpermitted sources.*.
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