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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: Michelle Wayment
Date Deposited: 20 Nov 2010 21:54
Last Modified: 23 Nov 2016 18:44
Item ID: 641

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