New Zealand Journal of Agricultural Research abstracts
Hydrological approaches to the delineation of critical-source areas
of runoff
M. S. Srinivasan
R. W. McDowell
AgResearch Ltd
Invermay Agricultural Centre
Private Bag 50034
Mosgiel 9053, New Zealand
m.srinivasan@agresearch.co.nz
richard.mcdowell@agresearch.co.nz
Abstract Five hydrological approaches, ranging
from empirical to physically based, were applied in two headwater
catchments (Silverstream and Glenomaru) in Otago, New Zealand, to
delineate the critical-source areas (CSAs) of runoff, the areas that
are directly linked to contaminant transport to surface waterways.
Comparison of observed and simulated flows for selected rainfall events
indicated that in one catchment (Glenomaru) the empirical approaches
performed better than physically-based approaches, while the converse
was true in the other catchment (Silverstream). However, spatial
mapping of simulated CSAs indicated that the approaches failed to
recognise areas where subsurface flows can potentially emerge to the
surface as seeps and springs on steep hillsides bordering the valleys.
The approaches were also evaluated based on the availability and
processing times of input data, representation of hydrological
processes, reliability of simulations, likely economic impact, and the
ease of implementing alternative management on the CSAs identified. Due
to minimal input data needs, minimal likely economic impact, and ease
of CSA management, empirical approaches may prove to be the most
useable approaches. Process-based approaches simulated unconnected and
poorly manageable CSAs that if managed would have a negative economic
impact. Economic analysis based on CSAs simulated using the empirical
approaches indicated that by managing CSAs to mitigate phosphorus
losses, significant decreases in phosphorus losses on a catchment scale
can be achieved without any loss in profitability, or even a gain.
However, we concluded that these approaches should be examined further
and the simulated CSAs validated to allow a better linkage of sources
of contaminants and runoff at a catchment scale.
Keywords critical-source areas; hydrology;
modelling; rainfall-runoff processes
A06059; Online publication date 24 May 2007; Received 31 October
2006; accepted 12 March 2007
New Zealand Journal of Agricultural Research, 2007, Vol. 50:
249—265
0028—8233/07/5002—0249 © The Royal Society of New Zealand 2007
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