The spatial variability of the wind in a sprinkler irrigated district: Implications for irrigation management

The spatial variability of the wind in the Montesnegros Irrigation District (MID), in Spain, has been analysed. From a wind series (2004–2007) registered by a reference weather station, a windspeed >2 m s−1 was observed about 50% of the time. During these periods about 70% of the time it blew from the northwest (known as the Cierzo).Wind was monitored at the reference site and at 17 sites throughout the MID. Using regression a series of the local wind velocities for the irrigation seasons 2004–2007 were estimated from the reference station data. Wind exposure for 39% of the MID area was found to be similar to that of the reference site; 25% were less exposed and 36% considerably more exposed.The spatial variability of the wind was used to calculate the suitable time for irrigation (STI, %) using Ador-Sprinkler software. STI was simulated for different irrigation systems and strategies: standard – Christiansen’s uniformity coefficient (CUC) > 84% and wind drift and evaporation losses (WDEL) ≤ 20%, restrictive – CUC ≥ 90% and WDEL ≤ 15% and relaxed – CUC > 80% and WDEL ≤ 25%. At the reference site, STI varied from 50 to 56% of the total time during the irrigation season time for standard strategy, from 68 to 77% for the relaxed strategy and 8 to 30% for the restrictive strategy. Excluding the restrictive strategy, the least exposed sites averaged 14% greater STI than the most exposed sites.

► How the spatial variability of the wind (SVW) affects the suitable time for irrigation (STI) is tested. ► An analysis and methodology are proposed for sprinkler irrigation districts in windy areas. ► SVW has consequences on the design, management and cost of the irrigation network. ► STI is miscalculated when SVW is ignored. ► SVW may affect STI as much as the irrigation management or the solid-set layout.