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Fresh water resources on the Planet is very limited!

One of the greatest challenges of the twenty-first century, doubling food production from already depleted resources!

Some quick facts ...

There will be a global food crisis in less than 30 years!
- Approximately 2.4 billion people worldwide experience moderate to severe food insecurity based on FAO 2022 report (Putting a number on hunger, FAO, 2022)
- The global food demand is projected to be doubled by 2050 (causes: population growth (30%), dietary shift mainly toward Meat (70%)! (Tilman and Clark , 2015)
- 42% of the world total irrigated area is located in only two countries, China (0.7 million km2) and India (0.67 million km2) with almost 40% of the world population (FAO 2016, Szilagyi et al., 2020)
We need irrigated agriculture to produce more food!
- Irrigated agriculture is at least twice as productive per unit of land as rainfed agriculture! (world bank, water in agriculture)
But then we would have a water crisis!
- 70% of freshwater withdrawal (over 90% in the Middle East and Southeast Asia) are devoted to irrigation globally! (Foley, et al., 2009)
- 40% of area equipped for irrigation globally and 60% within the united state relies on groundwater resources
- Groundwater depletion has doubled between 1960 to 2000

Climate change makes the situation even worse!

~70% of the areas that were irrigated in 1995 will require more irrigation water by 2070 (Döll and Siebert, 2002)
41% of irrigation water use is coming from the river's environmental flow requirement which has an adverse effect on the environment and natural habitats (Jägermeyr et al., 2017)
Irrigation is expected to increase by (+30 %) in Europe under a high emission scenario (Busschaert, metal., 2022)
The competition for water resources is already intense and is projected to worsen in the future, below map shows the ratio of the demand for water to the available water (water stress) (World resources institute, Aquaduct)

Irrigation impact on the climate system

Irrigation–Earth system interactions (Adopted from: Irrigation in the Earth system, MacDermid et al., 2023).

Irrigation has significant environmental impacts, both positive and negative:

Irrigation can transform areas from moisture-limited to energy-limited evapotranspiration, thereby influencing water and energy budgets (Taylor et al., 2012)
Rising groundwater-fed irrigation has increased downwind precipitation and discharge by up to 30% in High-plain and California central valley (DeAngelis et al., 2010 and Kustu et al., 2011)
Unexpected and least trivial one: the suppression of local precipitation by large-scale irrigation (Szilagyi et al., 2020)
Cooling the extreme hot days of year (Thiery et al., 2020, Lawston et al., 2020)
Delaying the onset of monsoons (Tuinenburg, 2013)
Creating humid heat waves that surpass human tolerance levels (Raymond et al., 2020; Wang-Erlandsson et al., 2022).

To enforce rule for governing water extraction we first need to monitor farmer's water withdrawal ...

in situ measurements are difficult because:

- It is labor-intensive and expensive even for the developing countries
- There are illegal water withdrawal from surface and groundwater
- Farmers may oppose or lobby against the installation of meters due to concerns about increased future regulation (Foster et al,., 2020)

Percentage of groundwater irrigation wells with an attached flow metering device for each state in the United States (Foster et al,., 2020)

we can use models to estimate the irrigation water use, however, ...

Dancing crop circles, seen by #Sentinel2. Küçükyıldız, Turkey. Images processed in @sentinel_hub (Annamaria Luongo)

Modeling irrigation is really challenging:

Cultivated crops are constantly changing (crop rotation)
Farmers' irrigation decision is not necessarily related to the crop water demand
Farmers often use rule of thumb method to determine when to irrigate, such as:
- Observing changes in plant characteristics, such as changes in color, curling of the leaves, and ultimately plant wilting
- Observing changes in the leaf temprature (a cool leaf during a hot day is an indicator of plant being well watered while
Most of the models estimate the required irrigation and not the actual irrigation

Crop cycles near #Bakersfield, CA, NDVI seen by #Sentinel2 created @sentinel_hub (Valtzen)

Irrigation studies

AMSR2 satellite soil moisture data is used to quantify irrigation amount.
SM2RAIN is able to capture irrigation pattern consistent with observations.
Nearly zero irrigation amount is estimated at the non-irrigated pixels.
Weekly signal are observed in soil moisture fluctuation at irrigated pixels.
Coarse resolution of microwave data hampers the usage of the model in small parcels.

Plot scale irrigation signal can not be detected using SMAP enhanced 9km product
The irrigation signal is more evident in the SMAP-Sentinel1 soil moisture variation (second moment of SM time series)
Human activity and land management over irrigated cropland can impact VWC and soil moisture retrieval
Using concurrent observations of vegetation water content can significantly improve soil moisture retrieval exclusively over the irrigated croplands

Finding:

Assimilating ~weekly SMAP-S1 soil moisture with a particle batch smoother (PBS) estimates significantly lower irrigation for non-irrigated vs. irrigated pixels
Irrigation is underestimated by 18.6%, likely due to losing part of the signal in SMAP-S1 1 km retrievals.
Synthetic studies demonstrate that knowing irrigation timing can greatly enhance simulation accuracy, achieving a 3% bias and an R2=0.95.

AgroTrack: Monitoring farmers irrigation decisions using Thermal remote sensing

AgroTrack captured significant fallowing of the fields post California 2021 Mega Drought

Our Irrigation studies in the social media

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