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Measuring Wind and Low-Relief Topographic Effects on Rainfall Distribution

Lentz, R.D. and Dowdy, R.H. and Rust, R.H. (1995) Measuring Wind and Low-Relief Topographic Effects on Rainfall Distribution. Applied Engineering in Agriculture. 11(2):241-248.

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Advances in agricultural technology are giving farmers the capability to selectively manage soils of smaller
and smaller areal dimension, and the capacity to alter management practices on the go. Farmers need to better
understand the nature of within-field variability if they are to adjust their management accordingly. We hypothesized that
wind interacts with low-relief topographic features and significantly alters rainfall distribution in the landscape. To
determine wind and topographic effects on rainfall distribution across agricultural landscapes, rainfall intensity
measurements have typically been made in situ. Problems associated with this method involve finding appropriate field
sites, observational uncertainties, and logistical complications. For a study of rain on low hills, we avoided such
problems by using a full-sized replica of a hill. Design and construction of this hill model are described. The apparatus
emulated the slope and summit components of a low hill, and summit elevation was adjustable [1 to 3 m (3 to 10 ft)]. It
was equipped with wind speed and direction sensors, and tipping-bucket flow-gages that measured natural precipitation
intercepted by catchments located on windward and leeward slope positions. It automatically maintained a windward
orientation during precipitation events, thus increasing the number of relevant measurements obtained in a given season.
Results, obtained over two field seasons, indicate that hydrological rainfall varied significantly across different portions
of the hill model.
On average, hill positions experiencing maximum intensity received 1.5x more rain than those positions with the least
precipitation. The rainfall pattern differed, depending on meteorological rainfall (intensity measured on level ground
beyond the hill model), incident wind speed, and hill-summit elevation. This study shows that rainfall can vary across
landscapes that include low-relief topographic features. The amount of variation is large enough to influence crop or
plant growth, and other soil processes.

Item Type: Article
NWISRL Publication Number: 0866
Subjects: Mass Import - unclassified
Depositing User: Users 6 not found.
Date Deposited: 20 Nov 2010 21:54
Last Modified: 23 Nov 2016 18:44
Item ID: 641