New Zealand Journal of Marine and Freshwater Research abstracts
Effects of small ponds on stream water quality and macroinvertebrate communities
John R. Maxted
Colin H. McCready
Auckland Regional Council
Auckland, New Zealand
email: john.maxted@arc.govt.nz
Mike R. Scarsbrook
National Institute of Water and Atmospheric
Research Limited
Hamilton, New Zealand
Abstract Six small constructed ponds (surface area 500–7500
m2, catchment area 28–158 ha) in rural and native forest catchments
in the Auckland region had poorer water quality than the streams they replaced.
Temperature (24°C) and dissolved oxygen (DO) (4 mg/litre) criteria were
exceeded for up to 46% and 84% of days, respectively, during a critical 40-day
summer period. The poor conditions found in ponds, even within undeveloped
native forest catchments, indicated that the physical characteristics of
ponds (e.g., lack of shade, organic sediments) affected water quality independently
of other factors (e.g., land use, riparian protection). The frequency and
severity of the exceedences were related to pond size, retention time, and
catchment land use; the most degraded conditions were found in rural ponds
with largest surface areas and longest retention times. Ponds affected water
quality and macroinvertebrate communities downstream. Exceedences of temperature
and DO criteria occurred more frequently and were more severe downstream
than upstream of ponds. Ponds in rural catchments increased mean daily stream
temperatures 3.1–6.6°C during the critical summer period, and temperature
differences were three times higher than those in bush catchments (0.8–2.0°C).
Elevated temperatures were observed for hundreds of metres downstream owing
to the slow rate of cooling (1°C/100 m), expanding the extent of adverse
effects well beyond the “footprint” of the pond. Macroinvertebrate community
composition (sample area 1–3 m2) and values of four commonly used
metrics appeared to be significantly affected by ponds in rural and native
forest catchments. These finding have important management implications that
should lead to modifications (e.g., breaching dams) of the estimated 4500
existing ponds in the Auckland region, where possible, and restrictions on
proposals for new “on-line” ponds.
Keywords ponds; small dams; water quality; temperature;
dissolved oxygen; macroinvertebrates; metrics; rural; New Zealand
M04122; Online publication date 15 August 2005 Received 22 June 2004; accepted
12 May 2005
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39:
1069–1084
0028-8330/05/3905-1069 © The Royal Society of New Zealand 2005
PDF file of entire paper: Print-quality (2517K) |
screen-quality (289K)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
