Abstract
Abstract To improve the water application uniformity for sprinkler irrigation on sloping land, indoor tests were conducted on an artificial slope (slopes of 0, 0.05, 0.10 and 0.15) to evaluate the effects of two riser orientations, vertical (VO) and perpendicular (PO) to the slope, on the uniformity of sprinkler rotation, radius of throw, water distribution of an individual sprinkler and the overlapped water application uniformity (WAU). Compared with the VO, the PO could effectively improve the water distribution on sloping land and minimize the risk of soil erosion. Additionally, the PO was superior in the WAU, and a rectangular arrangement could dramatically enhance the WAU at smaller sprinkler spacing, while larger acceptable sprinkler spacing was accepted in a triangular arrangement. The riser orientation and sprinkler spacing had the most significant effect on the WAU, followed by the slope and sprinkler arrangement, suggesting that the adjustment of riser orientation or sprinkler spacing was helpful in improving the WAU. However, from the aspects of investment cost and installation convenience for irrigation projects, the method of PO was recommended. Therefore, when designing the sprinkler irrigation systems on the slope, choosing PO is the simplest and most effective way to achieve good irrigation uniformity.
Highlights
China has 135 million ha of cultivated land, of which slope cultivated land accounts for 33.33 million ha, approximately 1/4 of the total cultivated land area
Sprinkler rotation uniformity is a key factor affecting the quality of sprinkler irrigation systems (Li & Kawano )
This finding indicated that when the riser was PO, the increase in terrain slope caused the sprinkler rotation uniformity to decrease, regardless of the minimal effect on the sprinkler rotation period, which was consistent with the findings of Nderitu & Hills ( ) and Li & Kawano ( )
Summary
China has 135 million ha of cultivated land, of which slope cultivated land accounts for 33.33 million ha, approximately 1/4 of the total cultivated land area. Sprinkler distribution is an important parameter in the design of irrigation engineering, and a key indicator for evaluating the water application uniformity of irrigation systems (Zhu et al ). Because of the terrain slope, the water distribution of a single sprinkler on sloping land is quite different from that on flat land. When no wind is present, the curves of water distribution on flat ground approximate a set of concentric circles centred on the location of the sprinkler, and the water application rates at the same distance from the sprinkler are almost equal. When the sprinkler is used on sloping land, the water distribution patterns approximate a set of eccentric circles, and at the same distance from the sprinkler, the water application rate for uphill is greater than that for downhill, thereby resulting in poor water application uniformity (Zhang et al )
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