ASSESSMENT OF IRRIGATION EFFICIENCIES OF AN AGRICULTURAL VALLEY WITH AN
OVEREXPLOITED AQUIFER USING REMOTE SENSING AND METEOROLOGICAL DATA
Abstract
Northern Mexico is characterized by semiarid climate, where limited
precipitation restricts crop production. Therefore, production needs
efficient irrigation techniques. Agriculture is a high water consumption
activity that in order to become more sustainable, demands knowledge of
irrigation efficiencies at the regional scale. In this work we present a
method to estimate irrigation efficiencies of croplands based on the
crops’ water demand obtained with remote sensing data. The study site is
located in an agricultural valley in northern Mexico in an area of
cornfields with approximately 47,000 ha under irrigation that lies on
top of an overexploited aquifer with a sustained declining water table
(averaging 2m/year of drawdown). Using Landsat 8 derived imagery from
the METRIC-EEFLUX site for the period between May 16 (emergence season)
to Nov 24 (harvest season) during the 2017 agricultural cycle, the Crop
coefficient (Kc), the reference Evapotranspiration (ET0) and the actual
Evapotranspiration (Eta) were obtained. To obtain daily values of ETa in
between the 16 day Landsat images interval, we used Kc obtained from its
relation with a normalization of the enhanced vegetation index (EVI),
and ET0 calculated using Penmann-Montheit fed with meteorological data
from weather stations in the vicinity of the area. Irrigation efficiency
was calculated using the quotient between ETa and water applied during
the agricultural cycle measured with volumetric gauges at the outlet of
the irrigation systems. For this study we monitored 5 parcels of corn
with different irrigation systems: two parcels with drip irrigation, one
with sprinkler irrigation and two with furrow irrigation. Results from
the irrigation efficiencies ranged from 47 % to 71 % and depend on
factors like parcel dimensions, irrigation schemes, scheduling and its
spatial uniformity. Crop yield data is used to discuss the impacts of
these factors on the irrigation efficiencies and the implications of
different water use strategies for the sustainability of water
resource-compromised regions. This methodology can be replicated in
extensive areas requiring knowledge of irrigation efficiencies for more
sustainable water management.