Measurement and modelling evaporation for irrigated crops in north-west Mexico

Abstract

Abstract:The surface energy balance and near-surface weather variables were measured during the complete growth cycle of cotton and wheat crops planted in two successive seasons in 1995±1996 at a ®eld site in the Yaqui Valley in Sonora, Mexico. These data were analysed in terms of a set of simple evapotranspiration models, which included the Penman±Monteith equation applied at both the hourly and daily time-scales and four semiempirical simpli®cations of that equation. The ®eld data were used to investigate and specify seasonal variations in the surface parameters (crop coecient or surface resistance) appropriate to these models. There was a marked dierence between the eective value of surface parameters for the (cotton) row crop and the (wheat) continuous-cover crop during and immediately after periods of¯ood irrigation. This dierence re¯ects the fact that wet soil and remnant pools of irrigation water are well exposed to the atmosphere for¯ood-irrigated row crops and that evapotranspiration rates are enhanced. It proved possible to incorporate a description of this phenomenon by including a simple, additional term in an otherwise traditional model of the seasonal variation in crop factor or surface resistance. Once the parameters in the various models had been optimized against ®eld data, all the models provided reasonable descriptions of the measured evapotranspiration. However, the Penman±Monteith equation applied at the hourly time-scale performed least well and required greater parameterization; hence, its use in this application is not justi®ed. At the daily time-scale, use of the Penman± Monteith equation or Shuttleworth's reference crop evaporation (with a crop factor) is arguably preferable to the others in that, having more realism, it provides a description in which the (calibrated) surface parameters are a purer measure of crop control. However, in terms of descriptive ability after local calibration, the Penman, Priestley±Taylor, and Makkink models proved superior in this study. The good performance of the Makkink formulation is particularly encouraging because this equation requires only incoming solar radiation, which can be readily estimated from remotely sensed data. #

Impact of climate change on irrigation requirements in terms of groundwater resources

“…In irrigated regions, accurate knowledge of recharge, evaporation, and transpiration is especially important for the sustainable management of scarce water resources (e.g., Gartuza-Payán et al 1998). Jiménez-Martínez et al (2009) estimated irrigation return flow in the Campo de Cartagena area of southeast Spain, a semi-arid region where irrigation return flow accounts for a substantial portion of recharge, and the fraction of applied water (irrigation plus precipitation) going to recharge ranged from 22% for a summer melon crop to 68% for a fall lettuce crop.…”

The use of remote sensing for estimating ET of irrigated wheat and cotton in Northwest Mexico

“…This factor is computed as the ratio of actual ET to reference ET and Garatuza et al (1998) has provided functions specifying the crop factor relevant for use with the Makkink equation (and others) in the Yaqui Valley irrigation scheme for crops that have continuous cover, specifically for wheat, and for row crops, specifically for cotton, both managed with furrow irrigation. Actual ET was measured using eddy covariance (EC) techniques which provide a direct measurement of both vapor flux (λET) and sensible heat flux (H ).…”

“…Following this approach, the energy balance closure errors for an experiment on the Yaqui Valley in 2000 (Rodriguez et al 2003) were estimated on the order of 30 W m −1 (1 mm day −1 , approximately). The K c functions were based on the widely used form for crop factors which describes the function in three linear sections: an initial rise as Garatuza et al (1998) and used in this study as compared to those proposed by the FAO Irrigation and Drainage Papers 24 and 56 (Doorenbos & Pruitt, 1977;Allen et al, 1998). Even though the values are similar, those from the FAO papers are useful only as a general guide and for comparison purposes because they represent specific conditions for a sub-humid climate and for non-stressed crops under excellent agronomic and water management conditions and achieving maximum crop yield.…”

“…Local observations of the crop factors and of the specific plant stage development should be used, wherever possible, to incorporate effects of plant variety, climate and cultural practices. Figure 3 shows the comparison between the estimated actual evaporation computed using satellite-derived solar radiation data in the Makkink equation with appropriate crop coefficients as suggested by Garatuza et al (1998) and the evapotranspiration measured with an eddy correlation system corrected by the Bowen ratio as suggested by Twine et al (2000) to ensure closure of the energy balance. This figure clearly shows the increase in evaporation following irrigation starting on day 98 in the case of the (cotton) row crop, and the progressive reduction in the rate of evapotranspiration as the crop loses vigor in the case of the wheat crop.…”

“…Figure 3. Comparison between the estimated actual evaporation presented as stars, these being the daily average values in W m −2 calculated using satellite-derived solar radiation data, the Makkink equation, and the appropriate crop coefficients as suggested by Garatuza et al (1998). Also shown, as dots, are field measurements of evapotranspiration made with an eddy correlation system.…”