Linking Water Treatment with Wetland Restoration - Restorative Redevelopment of Devastated Ecocultural Landscapes - page 370

systems where the first cells doing most of the work would be an area of reduced
human activity, and as one moved down through the wetland system increasingly
more human contact would be permitted and facilitated.
Treatment wetlands are essentially simple to operate but do require monitoring.
In terms of the water quality, it is necessary to gauge the performance of the system
by measuring the changes in contaminant concentrations as the water moves through
the system (Bays 2002). If the wetland is not working up to expectations, it's usually
an indication that there are issues, perhaps hydraulic ones, that are impeding perfor-
mance. Hydraulically, the main issues to ensure performance are to keep the water
moving and to maintain a constant depth or targeted depth range to avoid desicca-
tion, a critical concern in a place of high evaporation and aridity such as Iraq.
In terms of vegetation management, in the United States it is quite common
to encounter problems with herbivory. When wetlands are restored or created, in
almost no time at all “the word gets out” and animals begin to arrive, sometimes to
undesirable levels such that they completely eat their way through the vegetation that
has been installed. Managing nuisance herbivory can therefore often be an issue in
the long-term survival of shoreline or shallow-water plantings (Pouder and France
2002). In the restored Iraqi marshlands, however, we may actually want to encourage
herbivory. The water buffalo in Iraq are part of the ecosystem that's been established
there (Maxwell 1966; France 2007), and we would want to factor this in for the sus-
tainable operation of the system (Bays 2004).
Wildlife management also becomes a very significant issue in treatment wetlands.
Many of these wetlands function as secure oases free from disturbance and provide
a number of habitat types, important for maximizing the diversity of wildlife use
(France 2003). But most importantly, because nutrient concentrations are high in the
treated wastewater, the wetlands offer a rich availability of the food resources for
wildlife, which, as a result, may be there in abundance, sometimes at levels up to ten
times what would be expected to occur in natural wetlands (Bays 2004). Building
these treatment marshes therefore creates attractive habitat that is colonized almost
immediately, particularly in arid regions. For example, one year after their construc-
tion, the Tres Rios wetlands were fully colonized and producing high densities of
breeding birds (numbers increased from less than fifty birds to over eight hundred
birds per unit area within a single year; Bays 2004).
Design considerations to enhance wildlife habitat include a variety of morpho-
logical, hydrological, and ecological attributes (France 2003; Bays 2004). Variable
water levels—making sure water fluctuates over time—are important in enabling
wading birds to have access to the wetland. Alternatively, deep zones provide habitat
for waterfowl. A diversity of plants, including certain species with known qualities
that are beneficial to wildlife, can substantially increase biodiversity by building
vertical structure through adding perimeter trees for birds to perch upon, as well as
by building horizontal structure through making sure a gradient of habitat types or
riparian ecotone exists. Building islands to provide refugia from nest predators is
perhaps the most fundamentally useful and simple thing to do in a wetland construc-
tion project toward fostering avian diversity and abundance. And adding snags and
platforms, of course, is an easy and simple way in which to build hall-out habitat for
birds and turtles.