Control of Inflow Rates and Time of Cutoff

For a given field, two of the parameters in the performance functional relationships (5.135) and (5.136) remain constant—the length L and the slope S0. Several others may change from season to season and from irrigation to irrigation as a consequence of irrigation and farming practices—soil infiltration characteristics Ic, the shape of the


■ , i , ■ ,

100 m, 1 L/s \


400 m, 1 L/s

100 m, 2.5 L/s


200 m, 2.5 LVs


300 m, 2.5 L/s

400 m, 2.5 L/S

Figure 5.17. Distribution uniformity DU as affected by the standard deviation Sj of furrow entrance elevations for a furrowed level basin, considering different inflow rates and basin lengths. Source: [44].

furrow Fa, and the roughness of the surface n. Farmers can change these to some extent through tillage and other soil management and cultural or cropping practices. At the time of irrigation, the irrigator can only control the inflow rate qin and the time of cutoff tco. Thus, irrigator decisions to improve DU and ea can be expressed by the simplified functional relations

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