Download UNH Water Balance Model Structure - Single

PIAMDDI Meeting Preparation
University of New Hampshire
Water Balance Model
Richard B. Lammers
Danielle Grogan
Steve Frolking
Water Systems Analysis Group
Earth Systems Research Center
University of New Hampshire
Durham, NH, USA
13-14 December 2013
What happens as the river water moves to the river mouth?
Agriculture
Evapotranspiration
Direct human consumption
(Domestic and Industrial)
Diversions
Dams/Reservoirs
Wells/Groundwater mining
(Not counting water quality changes…)
2
UNH Water Balance Model Structure - Single Grid Cell
Irrigation Return
Precipitation
Evapotranspiration
Crop 2
Root
Depth
Crop 1
Snow pack
Excess
Surface
Runoff
Root Zone
Deep Soil Zone
Irrigation: 31 crops/land cover
(sub-grid fractions
modeled separately)
Ground
water
(Baseflow)
Water Transport
Model (WTM)
River
Water
Unsustainable
Irrigation
(Fossil ground water)
Global irrigation water demand:
Variability and uncertainties arising from agricultural and climate data sets
Drive WBM with:
Two climate reconstructions (NCEP and CRU; 1963-2002)
Simulated irrigation water withdrawal (km3 y-1)
Two maps of irrigated area (FAO & IWMI)
n = 159 countries
Minimum
0
Maximum
Precipitation (mm/y)
2000
1000
Irrig. Area
40°N
Eq.
Precipitation
FAO-reported national annual irrigation water withdrawal (km3 y-1)
Wisser et al (2008) Geophysical Research Letters, v.35, L24408
40°S
0
2
8
4
6
Irrigated Area (Mha)
Water Balance/Water Transport Model Runs
Includes: Reservoirs and Irrigation. Irrigation water applied with
100% efficiency (no loss back to system)
With and Without Inter-basin Transfers (Diversions)
When Diversions turned on (red line) more water is abstracted
from rivers for irrigation
Major
Diversions
Tracking the Benefits of Irrigation Inefficiencies
Surface Water
Rivers
Reservoirs
Deep Soil
Zone
Mined
Groundwater
(as needed)
crop
evapotranspiration
Evaporation
Irrigation water withdrawals
Return
flowpaths of
irrigation
inefficiencies
Inefficiency
losses
66%
34%
irrigation water demand (mm/y)
34% efficiency
680 km3/yr
irrigation water demand (mm/y)
34% efficiency
Mined groundwater (MGW) fraction of demand
34% efficiency
MGW = 48%
of demand
680 km3/yr
326 km3/yr
irrigation water demand (mm/y)
34% efficiency
Mined groundwater (MGW) fraction of demand
34% efficiency
MGW = 48%
of demand
680 km3/yr
68% efficiency
340 km3/yr
326 km3/yr
irrigation water demand (mm/y)
Mined groundwater (MGW) fraction of demand
34% efficiency
34% efficiency
MGW = 48%
of demand
326 km3/yr
680 km3/yr
68% efficiency
Can increased
irrigation efficiency
offset
groundwater mining?
340 km3/yr
irrigation water demand (mm/y)
34% efficiency
Mined groundwater (MGW) fraction of demand
34% efficiency
MGW = 48%
of demand
680 km3/yr
326 km3/yr
68% efficiency
68% efficiency
MGW = 52%
of demand
340 km3/yr
176 km3/yr
MGW use decreases (<50%) but its fraction of total demand increases.
Winners & Losers? In addition to
decreasing demand for mined groundwater,
would increasing irrigation efficiency shift
groundwater exploitation stress?
Gleeson
& Wada
ERL 2013
>100% over-exploited
90-100% critical
70-90% semi-critical
<70% safe
RED: Increased efficiency
increases relative reliance
on mined groundwater.
How to integrate?
Water Balance Model supplies water volume in space and time.
Irrigation =f(plant water demand, existing irrigated crops)
Can IAM tell us other factors controlling water demand?
- Changes in irrigated regions
- Market forces
- Technology
- Legal
Dams/Impoundments/Diversions = f(simple operating rules or specified)
Can IAM tell us if (or where) new engineering structures are built?
- future energy/water demand
- political process
Human water use
= f(Population)
Industrial water use = f(GDP)
Can IAM tell us
- How populations will change?
- How water use technology changes?
- Changes in desires/motivations of population for water use?