Small-stream buffers critical to health of ecosystems

Op-ed: Small-stream buffers critical

The Georgia General Assembly is considering a bill that will
greatly affect the health of streams across Georgia. Senate
Bill 460, a bill dealing with the piping of streams and stream
buffer variances, has passed the Senate and is currently being
considered in the House.

University of Georgia scientists have researched
watersheds and streams in Georgia and the Southeast for
decades. Much of this research has focused on small streams,
which
are the systems that will be affected by this legislation.

Senate Bill 460 proposes to allow piping of small streams with
less than 25 gallons per minute (gpm) average annual flow and
establishes general criteria for buffer variances. The 25 gpm
average annual flow is an arbitrary number without any
scientific basis.

While 25 gpm probably sounds like a small number, it’s not. An
average annual flow of 25 gpm translates to over 13 million
gallons per year, which could meet the water needs of over 175
people.UGA scientists are working on a study which the
legislature requested when it modified the trout stream buffer
legislation several years ago. The report from that study will
come out this summer.

Preliminary information from this research indicates:

1. In the Blue Ridge, an average annual flow of 25 gpm is
   generated by a watershed of about 16 acres. This only applies
   to the Blue Ridge. The watershed area generating that flow is
   likely to be significantly larger in other parts of the state.
   We estimate that watersheds of 30 to 45 acres would be needed
   to generate this flow in other parts of the state. Rainfall,
   topography, soils and geology all influence the amount of area
   required to generate this flow. These streams drain significant
   areas and should not be viewed as “wet weather ditches.”
2. In the Blue Ridge, a stream of this size would flow in
   a channel approximately six feet wide and three feet deep. This
   includes intermittent streams that would not have any flow at
   some times of the year but would fill the channel during the
   winter and also includes small streams that begin with a spring
   and flow year-round.
3. Often organisms such as mayflies, stoneflies and caddis
   flies
   are used as indicators of good water quality and are also
   excellent food for fish. In a Blue Ridge stream with 25 gpm
   average annual flow, there were numerous individuals from five
   different species in these indicator groups while in a piped
   stream there was only one individual in these indicator groups.
   In addition the total number of insects being supplied to
   downstream ecosystems from this piped stream was only 16 percent
   of what was being supplied from the unpiped stream. These
   insects
   are a critical source of food for downstream fish and other
   aquatic organisms.
4. We have already lost considerable mileage of small
   streams. For example, in the Upper Chattahoochee River,
   tributaries draining forest and pastures have about 2.2 miles
   of stream for every square mile of watershed. In urban and
   suburban watersheds where there has been considerable piping
   and filling, there are only about 1.5 miles of stream for every
   square mile of watershed. That means that 0.7 mile of stream
   per square mile has been lost in these watersheds. That is a
   one-third reduction in stream miles in these watersheds.
   If only a few small streams are piped in a watershed, that will
   not have dire consequences for downstream ecosystems. If,
   however, there is a general variance with no consideration of
   what has been done to other small streams in the watershed, the
   chances for widespread destruction of small streams is great,
   with significant consequences for downstream flooding, water
   supply, water quality and fisheries resources.

Decades of scientific research throughout the country have
demonstrated the services to society provided by intact small
streams. These services are eliminated when streams are
piped.

This is what we know about small streams:

1. They improve water quality. Think of them as the first
   line of defense. Excess nutrients entering waterways enter
   small streams, which are extremely efficient at removing those
   nutrients. They are much more efficient at nutrient removal
   than are larger, deeper channels. By eliminating those small
   streams you remove protection for waters further
   downstream.
2. They maintain water supplies. There are close
   connections between small streams and groundwater and they
   serve to recharge the shallow groundwater system. Our recent
   experiences with drought have shown water conservation to be a
   critical issue in Georgia, hence it is important to maintain
   these services of small streams.
3. They provide natural flood control. Because they slow
   the downstream movement of water, allow infiltration through
   the channel bottom to groundwater, and have access to a
   floodplain, these small channels reduce downstream flooding. In
   watersheds where small streams have been eliminated, downstream
   flooding increases.
4. Vegetated buffers around small streams trap sediment
   and other pollutants, slowing their rate of movement downstream
   and minimizing impact to water supplies.
5. They maintain biological diversity because there is a
   unique assemblage of organisms living in these small
   streams.
6. They sustain the food webs of downstream ecosystems.
   Small streams export material that serves as food for fish
   and other organisms living downstream.

The State is funding a study to look at this issue and the
results will be coming out this summer that will provide much
needed information on this issue. If the intent is to base
natural resource legislation on sound science, we need to allow
time for that scientific analysis to be completed.

(Mark Risse, Judy Meyer, David Radcliffe Liz Kramer Rhett
Jackson and William Bumback are scientists with water-related
responsibilities with the University of Georgia.)