With a spatial resolution of 500 meters and for periods
of 8 days, the MOD16A2 allows a detailed analysis of
water consumption patterns at a regional level, thus
contributing to the sustainable management of water
resources.
The ECOSTRESS sensor (Ecosystem Spaceborne
Thermal Radiometer Experiment on Space Station)
has been developed to measure the temperature
of the Earth’s surface with high precision. The
ECO3ETPTJPL product provides detailed data on In-
stantaneous Latent Heat Flux (W/m
2
), which is di-
rectly related to evapotranspiration, at a spatial resolu-
tion of approximately 70 meters. This high resolution
allows the study of specific phenomena at the local
and regional level, providing valuable information to
understand hydrological processes and the response
of ecosystems to changes in water availability.
We used the Application for Extracting and Ex-
ploring Analysis Ready Samples (AppEEARS, avail-
able at https://appeears.earthdatacloud.nasa.gov/) tool
to obtain ECOSTRESS evapotranspiration values.
Climatic data were obtained and processed with the
Climex program (
´
Angel Marqu
´
es-Mateu et al., 2023).
We performed all other statistical analysis, mapping
and graphing operations with the R program (R Core
Team, 2021).
4 METHODS
4.1 Preliminary Analysis of Census
Data
The SIAP data were analyzed to determine which mu-
nicipalities have important irrigation areas (more than
10,000 ha) dominated by a single crop (more than
80%, during 2003-2023) and whether a change in
dominant crop occurs. In this preliminary study, we
sought a more straightforward case to avoid dealing
with an area with different crops with different spec-
tral responses and planting and harvesting schedules.
4.2 Analysis of Agricultural Dynamics
and Estimation of the Sown Area
We prepared time series with MODIS (ET and NDVI,
2002-2023) and ECOSTRESS (Latent Heat Flux,
2018-2020) data. We selected 30 random points in ir-
rigation areas and drew graphs showing the temporal
variations of these variables, allowing us to observe
the areas sown or not in the two cycles.
In the next step, we evaluated to what extent re-
mote sensing data at different spatial resolutions allow
evaluation of the sown area during the winter/autumn
cycle. We computed the correlation coefficient be-
tween the sown area reported by the SIAP and in-
dices obtained from the images as the sum of the
NDVI and ET values in the irrigation areas during
the autumn/winter cycle. An unmixing exercise of
the MODIS images was also carried out to estimate
the sown area obtained from the Landsat image for
the same date.
To estimate the evapotranspiration of croplands,
we used the Blaney-Criddle method (Blaney and
Criddle, 1950) because it is accurate enough and only
requires temperature data (Equation 1).
ET
c
= K
c
∑
p(0.457T
mean
+ 8.128) (1)
Where: Et
c
is the crop evapotranspiration (mm),
T
mean
is the mean daily temperature, p is the mean
daily percentage of annual daytime hours, and K
c
is
the crop coefficient.
We obtained the temperature from data from cli-
matological stations for 1981-2010. We chose sta-
tions that best represented the climatic conditions of
irrigated areas. We used crop coefficients from local
and international sources (Allen et al., 1998;
´
Angeles
Hern
´
andez et al., 2017; INIFAP, 2001). We compared
these ET values with those obtained from the analysis
of MODIS and ECOSTRESS images.
5 RESULTS
One municipality that met the search criteria was
P
´
enjamo in the State of Guanajuato. The dominant ir-
rigated crop (more than 80% during 2002-2014) was
wheat, and from 2016, wheat and barley. The to-
tal irrigation area sown during 2003-2022 varied be-
tween 12,000 and 34,500 ha (autumn-winter cycle)
and 18,000 and 37,000 ha (spring-summer cycle).
As shown in Figures 3 and 4, MODIS time series
(NDVI and ET) allow crop growth to be clearly ob-
served in both cycles.
The ECOSTRESS data obtained for the same
points were very noisy. We observed very high la-
tent flux values, which the uncertainty layer did not
allow to eliminate (Figure 5).
The NDVI was calculated based on a Landsat 8
image from March 2, 2020, when the contrast be-
tween cultivated and non-cultivated areas appeared
strongest. We determined visually that the value of
0.3 separated the areas with crops. The binary crop
map obtained by thresholding indicates a cultivated
area of 13,650 ha, while the SIAP reports a very close
value (13,905 ha). The Landsat binary crop map was
overlaid with the MODIS NDVI image of the same
Assessment of Census and Remote Sensing Data to Monitor Irrigated Agriculture in Mexico
183