Real-time Sierra Nevada water
monitoring system
60
Context & need
Based on SCA depletion and degree day calculation
50
Missing elements & enabling technology. The current
ground-based measurement system for snow, designed
for statistical water-supply seasonal forecasts, does not
provide representative measurements of snow depth or
water equivalent. A system of continuous representative
measurements using low-cost technology, when blended
with accurate satellite snow-cover data, can provide an
accurate, real-time estimate of spatial snow amounts.
Three elements have recently come together that make
deployment of a full-basin-scale measurement &
information system feasible: i) accurate, sustained satellite
estimates of snow covered area across mountain
watersheds, ii) reliable, low-cost sensors & telemetry
systems for snow and soil moisture, and iii)
cyberinfrastructure advances to integrate data & deliver it
in near real time.
7
Importance. Climate change introduces uncertainty into
water forecasts that are based on historical statistical
relationships, with errors greatest for conditions further
from the historical mean. Increasing pressures on
mountain water supplies & flood control also make
accurate forecasting more important to water decision
makers than in the past. Accurate, real-time estimate of
spatial snow amounts are critically needed & when
available will provide an unprecedented, quantitative
picture of snowcover across Sierra Nevada watersheds,
which will inform water supply estimates, flood forecasts &
resource management decisions. Soil moisture is
emerging as a critical response variable, which exhibits
basin-scale variability with snow
Volumne snowmelt, 10 m
3
3450
40
3150
30
2850
20
2550
10
2250
1950
0
3/1/04
4/1/04
5/1/04
6/1/04
7/1/04
Daily snow water equivalent estimates by elevation
band (cumulative amount melted) for Tuolumne R.
basin, 2004. Melt is based on time series satellite
snowcover & energy balance, estimated after snow
has depleted. Accurate real-time forecast s require
augmentation of existing, sparse snow telemetry
data to estimate snow water equivalent across
basin.
Bias in April 1 forecasts (underforecast) for July-April
unimpaired runoff for 15 Sierra Nevada basins. 2005 was
about 150% of average accumulation, i.e. a wet year.
Conceptual design. A ground-based basin-scale design
will consist of instrument clusters located along transects.
The clusters will sample the main variables controlling
snow distribution & melt, i.e. elevation, aspect, vegetation
& in some cases, distance to a major ridge (wind effects).
Each cluster will extend over 1-2 km distance, & include
10-20 snow depth & soil moisture measurement nodes.
On the order of 20 clusters will be deployed across a
basin, taking advantage of existing snow & meteorological
sites where possible.
UC contact: Roger Bales, Sierra Nevada Research Institute,
UC Merced, [email protected]
Snow depth sensor with radio
Real-time Sierra Nevada water
monitoring system
Scenario for ground-based
instrument deployment in
American River basin, with
existing instrumentation, land
ownership & wilderness
Snow course
Meteorological station
Snow pillow
Wilderness boundary
Basin boundary
% SCA
76-100
51-75
26-50
1-25
Highway
USFS land
New instrument cluster
Use of snow products in decision support
Interpolated snow water equivalent from ground-based
measurements, masked by satellite snow-covered
area, gives much more accurate estimate of
snowpack water volume across a basin than does
use of point snow pillow data alone.
Expected outcomes. Deployment of a full-scale basin
system will inform water management in that basin, form
the core of a new water information system for the Sierra
Nevada, serve as a testbed for further deployment &
provide data needed for research & development to
modernize forecasting & decision-support systems. The
resulting approach for estimating snowpack is robust
relative to climate change, will improve forecast accuracy
& will serve the state for decades to come.
Installing soil moisture probes