Methodology
Which groundwater-irrigated crops contribute to aquifer stress in California and the High Plains?
Laurent Esnault 1 , Tom Gleeson 1 , Yoshihide Wada 2 , Jens Heinke 3 , Dieter Gerten 3 , Elizabeth Flanary 1 , Marc F. P. Bierkens 2,4 ,
Ludovicus P. H. van Beek 2
Introduction
Fraction of recharge needed to sustain environmental flow requirements
47%
Net blue water requirement Total irrigation efficiency
Irrigated acreage
Proportion of irrigated
acreage
irrigated with groundwater
Groundwater abstraction:
Groundwater footprint:
“the area required to sustain groundwater use and
groundwater-dependent
ecosystem services of an aquifer”
Results
corn 12%
sorghum
1% cotton 1%
grass 1%
hay 31%
safflower 2%
pulses 1%
rice 25%
sunflower 1%
wheat 2%
pasture 23%
corn 29%
sorghum 1%
grass 1%
hay 43%
safflower 2%
pulses 1%
rice 2%
sunflower 1%
wheat
1% pasture 19%
corn 26%
sorghum 1%
grass hay 1%
safflower 46%
2%
pulses 1%
rice 3%
sunflower 1%
wheat 2%
pasture 17%
corn 23%
sorghum 1%
cotton hay 18%
40%
safflower 1%
pulses 1%
wheat 1%
pasture 15%
corn
19% sorghum 2%
cotton 29%
grass 1%
hay 41%
wheat 3%
pasture 5%
1
Department of Civil Engineering, McGill University, Montreal, Quebec, Canada |
2Department of Physical Geography, Utrecht University, Utrecht, The Netherlands |
3Potsdam Institute for Climate Impact Research, Research Domain of Earth System Analysis, Potsdam, Germany |
4Unit Soil and Groundwater Systems, Deltares, Utrecht, The Netherlands
corn (grain)
58%
corn (silage) 2%
hay beans 20%
3%
soybean 6%
sugarbeets 3%
sunflower 1%
wheat 2%
pasture 5%
corn (grain)
50%
corn (silage)
3%
sorghum 5%
cotton 2%
hay 17%
soybean 2%
wheat 16%
pasture 4%
corn (grain)
8% corn (silage) 3%
sorghum cotton 6%
60%
hay 11%
peanut 3%
wheat 5%
pasture 5%
recharge 30%
net blue water requirement
17%
proportion of irrigated acreage
irrigated by groundwater
9%
application system efficiency
35%
conveyance system efficiency
9%
Crop type contribution to the agricultural groundwater footprint in the aquifers of the Central Valley
Extent of the agricultural groundwater footprint in the aquifers of the Central Valley
Actual extent of the aquifer
Parameter contribution to the uncertainty of the agricultural groundwater
footprint in the Central Valley
Crop type contribution to the agricultural groundwater footprint in the aquifers of the
High Plains
Extent of the agricultural groundwater footprint in the aquifers of the High Plains
recharge 34%
net blue water requirement
12%
proportion of irrigated acreage irrigated by groundwater
15%
irrigated acreage
1%
application system efficiency
28%
conveyance system efficiency
10%
Parameter contribution to the uncertainty of the agricultural groundwater footprint in the High Plains
Actual extent of the aquifer
• crops grown for cattle-feed and ethanol production are the biggest stressors → impact of meat consumption and economic policies on aquifer stress
• lower groundwater footprint than previously estimated in the Central Valley, likely due to large-scale surface water diversions increasing artificial recharge
• recharge and irrigation application efficiency are among the most uncertain measured parameters → need for improved data
Conclusion
100 km
200 km
0.3 ± 0.2
1.7 ± 1.0 1.3 ± 0.8
1.5 ± 0.9 0.9 ± 0.5
5.2 ± 2.3
11.2 ± 5.1
15.4 ± 8.3 Groundwater recharge
• at county scale (cty)
• at aquifer scale (aq)
• global rate of groundwater depletion has more than doubled since the 1960s
• groundwater accounts for ~40% of the total consumptive irrigation water use globally
• agriculture consumes most of the groundwater abstracted
→ But how do specific crop types impact groundwater resources of a specific aquifer system?
Case study:
• USA has the 2
ndhighest rate of groundwater abstraction in the world
• the Central Valley (California) and High Plains aquifer systems:
– have the highest rate of groundwater abstraction in the USA
– respectively represent 7% and 11.7% of the USA’s $300 billion in agricultural revenue (2007)
Global model Global model
Local model
downscaling weighting
downscaling weighting
