Tom Brown and Travis Warziniack
Rocky Mountain Research Station
U.S. Forest Service
Collaborators
Jorge Ramirez and Vinod Mahat
Colorado State University
RPA webinar March 30, 2017
• The Renewable Resources Planning Act (RPA) of 1974
mandates a decennial nationwide “analysis of present
and anticipated uses, demand for, and supply of the
renewable resources”.
• A 1990 amendment to the RPA act mandates “analysis
of the potential effects of global climate change on the
condition of renewable resources”.
• Provides a snapshot of current U.S. forest and rangeland
conditions and trends
• Identifies drivers of change
• Projects 50 years into the future (2010-2060 for the Update).
• Includes analyses of the following resources:
•
•
•
•
•
Land resources
Forest resources
Urban forests
Forest products
Forest carbon
•
•
•
•
Rangeland resources
Water resources
Wildlife, fish, and biodiversity
Outdoor recreation
1. Estimates of past mean annual water yield across
the contiguous 48 states (the “U.S.”)
2. Assessment of future water supply vulnerability in
the U.S.
3. Analysis of options for lessening future water supply
vulnerability
The Water Assessment relies critically on data from other agencies:
USGS, NOAA, DOE, COE, USBR, ERS
Mean annual water yield
Water yield = precipitation ─ evapotranspiration
50% yield
18 water resource regions
5% yield
Mean annual water yield 1981-2010
Estimated with the VIC model at 1/8th degree scale (≈12km2 cells)
Land owner
West
Plains Midwest South Northeast
All
Percent of land area
Forest Service
21
2
6
7
2
11
Other federal
29
2
1
3
1
13
State & private
50
96
93
90
97
76
Percent of mean annual water yield
Forest Service
49
3
6
8
3
18
Other federal
14
2
1
3
1
5
State & private
37
96
93
89
97
77
Regions
Ownership from 2005 Federal Lands of the
United States database of the National Atlas.
For more detail go to the 2015 RPA Update, or to https://www.fs.fed.us/rmrs/documentsand-media/really-mean-annual-renewable-water-supply-contiguous-united-states
Land cover
data set
West
Plains Midwest South Northeast
All
Percent of all land that is forest
NLCD
23
8
25
44
58
26
LandFire
27
11
27
50
60
29
FIA
30
11
28
66
66
34
Percent of mean annual water yield from forest
NLCD
58
19
28
46
60
46
LandFire
64
22
30
51
62
50
FIA
75
27
30
66
69
59
Regions
Why the differences by land cover data set?
• In the Northeast, South, and Midwest most differences are due to riparian vs. forest.
• In the Plains and West most differences are due to range vs. forest.
2006 NLCD: deciduous forest (41), evergreen forest (42), mixed forest (43).
2012 LandFire: EVT_PHYS (Physiognomy): conifer, conifer-hardwood, hardwood, hardwood-conifer, exotic tree-shrub if EVT_GP = 707.
2008 FIA forest cover.
Estimate the probability of water shortages in basins throughout the U.S.
under alternative future socioeconomic and climatic conditions,
assuming:
– Only renewable water is available for use (i.e., no groundwater
mining).
– Instream flow constraint of 10% of mean annual flow.
– No major new adaptations to impending shortages beyond likely
improvements in water use efficiency and likely decreases in
irrigated area in the West (e.g., reservoir storage and trans-basin
diversion capacities are assumed to remain at current levels).
Spatial scale: 98 basins called ASRs
Time step: annual
Why do a nationwide assessment?
Modeling approach - general info. for all RPA assessments
GCMs and
downscaling
model
Water
yield
Climate
(T, P, ETp)
Water yield
model
IPCC scenarios,
updated and
disaggregated
Socioeconomic
conditions
(population,
income, etc.)
Water routing
model
Water flow paths
and management
infrastructure,
instream flow
constraint, etc.
Water
demand
Water
supply
Vulnerability
Water demand
model
IPCC 4th Assessment drivers
Socioeconomic/GHG emission scenarios
A1B
Population
Medium
growth
Economic
High
growth
Temperature Medium
increase
A2
B2
High
Low
U.S. population
Low-medium Low
High
Low
Climate models (GCMs)
U.S. mean temperature
A1B
A2
B2
CGCM31 MR
CGCM31 MR
CGCM2 MR
CSIROMK35
CSIROMK35
CSIROMK2
MIROC32 MR MIROC32 MR HADCM3
Modeling approach – water yield
GCMs and
downscaling
model
Water
yield
Climate
(T, P, ETp)
Water yield
model
IPCC scenarios,
updated and
disaggregated
Socioeconomic
conditions
(population,
income, etc.)
Water routing
model
Water flow paths
and management
infrastructure,
instream flow
constraint, etc.
Water
demand
Water
supply
Vulnerability
Water demand
model
Water supply—future water yield
Change (cm/yr) in projected water yield from current period to
the 2060 period for two of the nine futures
A2-CSIRO
The 2060 period is 2051 to 2070.
B2-HADN
Modeling approach – water demand (desired consumption)
GCMs and
downscaling
model
Water
yield
Climate
(T, P, ETp)
Water yield
model
IPCC scenarios,
updated and
disaggregated
Socioeconomic
conditions
(population,
income, etc.)
Water routing
model
Water flow paths
and management
infrastructure,
instream flow
constraint, etc.
Water
demand
Water
supply
Vulnerability
Water demand
model
Water demand—aggregate consumption
Past and projected annual water consumption in the U.S.
by water use sector, scenario A1B, no climate effects
IR = agricultural irrigation, TF = freshwater thermoelectric, IC = industrial and
commercial, DP = domestic and public, LA = livestock and aquaculture.
Water demand—future desired consumption
Percent change in projected water consumption from current
period to 2060, selected futures
A2
B2
Without
climate
change
Irrigated area
Water demand—future desired consumption
Percent change in projected water consumption from current
period to 2060, selected futures
A2
B2
Without
climate
change
A2-CSIRO
With
climate
change
B2-HADN
Modeling approach – water allocation
GCMs and
downscaling
model
Water
yield
Climate
(T, P, ETp)
Water yield
model
IPCC scenarios,
updated and
disaggregated
Socioeconomic
conditions
(population,
income, etc.)
Water routing
model
Water flow paths
and management
infrastructure,
instream flow
constraint, etc.
Water
demand
Water
supply
Vulnerability
Water demand
model
Water supply (i.e., water available for delivery)
Water potentially available for delivery to off-stream uses in an ASR
in a given year =
water yield within the ASR
+ inflow from upstream ASRs
+ net trans-basin diversion into the ASR
+ water left reservoirs in the ASR or upstream ASRs in the previous
year (after accounting for reservoir evaporation)
– required in-stream flow of the ASR
– required release from the ASR to satisfy downstream demands.
ASR reservoir storage capacities
(million acre feet)
ASR interconnections
Natural flow path
Trans-basin diversion
Mexico commitment
Modeling approach – vulnerability to shortage
GCMs and
downscaling
model
Water
yield
Climate
(T, P, ETp)
Water yield
model
IPCC scenarios,
updated and
disaggregated
Socioeconomic
conditions
(population,
income, etc.)
Water routing
model
Water flow paths
and management
infrastructure,
instream flow
constraint, etc.
Water
demand
Water
supply
Vulnerability
Water demand
model
Vulnerability—in 2060, A1B scenario
Probability of water shortage for three climate models
CGCM model
MIROC model
CSIRO model
Vulnerability—in 2060, A2 scenario
Probability of water shortage for three climate models
CGCM model
MIROC model
CSIRO model
Vulnerability—in 2060, B2 scenario
Probability of water shortage for three climate models
CGCM model
MIROC model
CSIRO model
Vulnerability—in 2060, range
Min and max probability of shortage across the nine alternative
futures for each ASR
Minimums
Maximums
1. Impose a change in some aspect of water demand or supply (such as
bigger reservoirs).
2. Rerun the water routing model.
3. Compare the resulting estimates of the probability of water
shortages to those obtained without the change.
Large (69-ASR) network
This was done
for the large
network only.
Six adaptation options
• Decreases in thermoelectric water consumption
• Larger reservoirs
• Further decreases in irrigated area
• Larger trans-basin diversion canals/tunnels and more
flexibility in meeting demands served by diversion
• Lower in-stream flow constraint
• Groundwater mining
Average annual past groundwater mining
as a percent of total annual withdrawal
Effect of selected adaptations on vulnerability in the
2060 time period*, A1B-CGCM future
* 2051- 2070
One additional adaptation: water trades
Projected mean annual water transfers from ag to urban uses in 2060 period,
assuming no legal constraints or transaction costs
-4%
-2%
+3%
-5%
+9%
+1%
Numbers are the transfer
amounts as a percent of
pre-transfer within-basin
consumptive use,
A1B-CGCM future.
+.3%
+.4%
-.3%
-.1%
Wrap-up—key findings and implications
• Population increases alone will not cause a large increase in water
demand, because of decreasing withdrawal rates and reductions in
irrigated area in the West.
• In many basins, climate change will decrease water yield and increase
water demand.
• Vulnerability increases typically are caused by a combination of
decreasing water yield and increasing water demand.
• Much uncertainty remains about the specific level of vulnerability for
most basins (as indicated by the differences among the different
scenarios and GCMs).
• In general, the larger Southwest, including parts of California, the Great
Basin, and the central and southern Great Plains, are likely to
experience increasing water supply vulnerability in the absence of new
adaptation measures.
• Adaptation will be essential, but large increases in reservoir storage
capacity are typically not the answer.
• This will lead to increased pressures to decrease in-stream flow,
increase groundwater mining, and further improve water use efficiency.
Enhancements for the 2020 water vulnerability assessment
• Newer climate simulations.
• Improved water yield model (VIC).
• Improved water demand model.
• Finer spatial resolution (204 HUC-4 basins).
• Finer temporal resolution (months).
Projected future water yield, using newer climate projections
Multi-model average percent change in mean annual water yield
from the 2000 period to the 2080 period
RCP 4.5
RCP 8.5
Some pubs on the 2010 water assessment and the update
Brown, Thomas C., Romano Foti, and Jorge A. Ramirez. 2012. Water resources. Chapter 12 of
Future of America’s forests and rangelands: Forest Service 2010 Resources Planning Act
Assessment,” General Technical Report WO-87, U.S. Forest Service, Washington, DC. 198 p.
Foti, Romano, Jorge A. Ramirez, and Thomas C. Brown. 2012. Vulnerability of U.S. water supply to
shortage: a technical document supporting the Forest Service 2010 RPA Assessment. Gen.
Tech. Rep. RMRS-GTR-295. Fort Collins, CO: U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station. 147 p.
Brown, Thomas C., Foti, Romano, Jorge A. Ramirez. 2013. Projected freshwater withdrawals in
the United States under a changing climate. Water Resources Research 49(3):1259-1276.
Foti, Romano, Jorge A. Ramirez, and Thomas C. Brown. 2014. A probabilistic framework for
assessing vulnerability to climate variability and change: the case of the US water supply
system. Climatic Change 125 (3-4): 413-427.
Foti, Romano, Jorge A. Ramirez, and Thomas C. Brown. 2014. Response surfaces of vulnerability
to climate change: the Colorado River Basin, the High Plains, and California. Climatic Change
125(3-4): 429-444.
Brown, Thomas C., Travis Warziniack, Vinod Mahat, and Jorge A. Ramirez. 2016. Water resources.
Chapter 10 of Future of America’s forests and rangelands: Update to the Forest Service 2010
Resources Planning Act Assessment, Gen. Tech. Rep. WO-94, U.S. Forest Service, Washington,
DC.
Thank You
[email protected]