WATER SECURITY INDICATOR MODEL
GLOBAL WATER MONITOR AND FORECAST
The ISciences Water Security Indicator Model (WSIM) monitors and forecasts water anomalies on a near global basis. Each month, WSIM documents current anomalies and provides forecasts with lead times from 1-9 months. WSIM products include data, visualizations, and reports.
WSIM includes algorithms to assess the impacts of water anomalies on people, agriculture, and electricity generation. WSIM has been run continuously since April 2011 and has been validated against subsequent monitoring based on observed data.
ISciences has released WSIM as open-source software, enabling source code transparency and collaboration. Making WSIM open-source allows the full functionality of our Water Security Indicator Model to be embedded in environments that use proprietary data. For more information about working with the open source version of WSIM visit https://wsim.isciences.com/working/index.html.
WSIM identifies regions with significant water anomalies - either deficits or surpluses relative to historically expected quantities. At ISciences we have been using a 1950-2009 baseline period, but users of the open-source WSIM can specify alternate periods.
Regions with deficits are shown in increasing intensity of red; surpluses are shown in blue. Purple regions exhibit aspects of both deficit and surplus. A good example is a river that runs through a region with below normal soil moisture level, but where the water level is high due to a larger than normal spring snowmelt in the headwaters.
WSIM calculates deficits based on a composite of soil moisture anomalies, evapotranspiration deficit anomalies, and upstream runoff anomalies. Surplus anomalies are based on a composite of local runoff and upstream runoff anomalies.
Anomalies are expressed in terms of "return period." The return period describes how rare the deficits or surpluses are relative to expectations. For example, an anomaly with a return period of 10 years would be expected to occur once every 10 years on average based on historical distributions.
ISciences has used WSIM with historical data that begins in January 1950. This allows us to assess current and forecast anomalies in historical context. For example, Brazil is not typically considered drought prone. However, frequent large, exceptional droughts over the past 15 years are a clear departure from past trends. Notable examples include 2002, 2005, 2007, 2010, 2012, 2013, and 2014. The 2014 drought forced water rationing in Sao Paulo, required extensive use of imported natural gas to generated electricity that would normally have been provided by hydropower, and significantly reduced production of several agricultural products.
WSIM makes use of temperature and precipitation data, physical geography data, and human geography data:
- Past, current, and forecast temperature and precipitation. Forecasts are derived from an ensemble of 28 NOAA CFSv2 forecasts issued the last week of each month. This ensemble is carried all the way through the processing chain and allows us to characterize uncertainty in the forecasts.
- Physical geography including soil properties, elevation, and routing networks.
- Human geography including water withdrawals by sector and the fraction of withdrawals that is consumptive by sector.
WSIM includes a reduced form hydrological model that estimates a suite of physical quantities including soil moisture, runoff, evapotranspiration, evapotranspiration deficit, snow water equivalent, and total flow accumulated runoff. Values are computed on a monthly basis from January 1950 through present, and into the future with lead times of 1-9 months. These quantities are combined with estimates of total withdrawals and consumptive use to produce estimates of the water withdrawal ratio (withdrawals relative to renewable supplies with upstream consumptive use removed) and the water reuse index (fraction of available water previously used and discharged upstream). Coverage is near global (only excluding Antarctica and most of Greenland) at 0.5° x 0.5° resolution (approximately 55 km x 55 km at the equator).
This deep history allows us to characterize historical distributions and estimate the return periods for past, present, and forecast conditions. Return periods are calculated using 1, 3, 6, 12, 24, 36 and 60 month integration periods to characterize short and long term anomalies.
WATER AND AGRICULTURAL SECURITY
WSIM can also generate an agricultural assessment that evaluates the degree to which water anomalies restrict agricultural production. The WSIM agricultural assessment uses data about cultivation areas, crop calendars, and reservoir capacity to provide geographically explicit "loss risk" maps. This capability has been validated against USDA yield and insurance data for the coterminous United States.
NOTE: The initial open-source release of WSIM does not include agricultural assessment. We expect to provide this feature in future releases.
WATER AND ELECTRICITY SECURITY
Similar in concept to the WSIM agricultural assessment, WSIM can produce an electricity assessment that evaluates the degree to which water deficits restrict electricity production from hydropower and thermal plants (including nuclear). The WSIM electricity assessment considers upstream reservoir capacity and consumptive use, fuel stock and cooling technology, and downstream water stress.
NOTE: The initial open-source release of WSIM does not include electricity assessment. We expect to provide this feature in future releases.
ISciences also provides customized assessments of the impacts of water anomalies on people, agriculture, and electricity generation. Additional information and pricing is available upon request.
For more information contact firstname.lastname@example.org.