| Popis: |
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. |
