Storm runoff characteristics of grazed watersheds in eastern Oregon
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Authors: D. A. Higgins, S. B. Maloney, A. R. Tiedemann, and T. M. Quigley
Date: 1989
Journal: Water Resources Bulletin
Volume: 25
Number: 1
Pages: 87-100
Summary of Methods: The differences in storm runoff and peak discharges between grazing intensities and vegetation types on 13 small watersheds within Blue Mountains of eastern Oregon were investigated. The pastures received one of four management strategies: 1) Strategy A - no grazing, 2) Strategy B -season-long grazing without uniform livestock distribution, 3) Strategy C - grazing with uniform livestock distribution and 4) Strategy D - intensive grazing. A moderate (50%) utilization level was the goal on all grazed pastures. Vegetation was put into two classes: Western larch-Douglas-fir (nine watersheds), and other (four watersheds representing fir-spruce, lodge pole pine, mountain meadow, and ponderosa pine). Rainfall and runoff data from 485 storms during the summers of 1979-1984 were used to estimate storm runoff volumes (SF), peak flows (QP), peak flow above initial flow (QPI) and total storm rainfall (PPT).
Article Summary / Main Points: Stormflow (SF) ranged from 0.0001 to 0.3519 inches and rarely exceeded more than 2% of rainfall on all watersheds and grazing regimes. In spring, peak discharge (QP) never exceeded the annual peak discharges that occurred from melting snow due to high evapo-transpirational demand and high infiltration rates. Grazing intensity levels and vegetation class had no effect on storm runoff and peak flows.The larch-Douglas-fir ecosystem was less reactive to rainfall compared to other vegetation types. In the larch-Douglas-fir vegetation class, as PPT and QI increased, the rate of increase in SF and QPI was slower than in other vegetation. Infiltration rates were highest in larch (3.5 in/hr), mountain meadow (3.3 in/hr), Douglas-fir (3.2 in/hr) and lowest in ponderosa pine.
Vegetation Types: Intermountain Grasslands (includes Palouse Prairie and Canyon Grasslands) Ponderosa Pine Woodlands Sagebrush Steppe
MLRA Ecoregions: 43C Blue and Seven Devils Mountains 9 Palouse and Nez Perce Prairies
Agrovoc Control Words: Ecosystems Grazing Watersheds
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: stormflow, peak flow, hydrograph separation, base-flow rise rate, surface water hydrology
Annotation: These results are applicable to many types of rangeland watersheds and small pastures. Since the sampling was done across 13 watershed areas and on different vegetation types such as Sagebrush Steppe, Ponderosa Pine, and Intermountain Grassland makes the results of this study widely applicable to rangelands from many areas.
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