You’ve seen a lot of news from us lately about wind and solar, but 3TIER got its start — and is a leader in — forecasting for the hydro power industry. Here are briefs on a few recent journal articles by 3TIER hydrology experts.

Water, Water Everywhere

In October 2007, record rains caused flooding on the Congo river that killed more than 400 people and displaced many more. The Congo has overrun its banks — causing floods, landslides, destruction, and death — every couple of years for the past few decades, but history does not make a life-sparing prediction system.

To improve flood forecasting in places like the Congo where hydrological stations are scarce, Andy Wood (who recently joined 3TIER but retains an affiliate faculty position at the University of Washington) and colleagues evaluated three global precipitation datasets to see how well they predicted floods in nine of the world’s large river basins. The authors fed each dataset and other meteorological factors into the variable infiltration capacity hydrology model, producing a representation of the period from 1997 to 1999, which they then compared to the actual hydrologic values for that time span. While each of the three datasets had different strengths and weaknesses, the authors favored the ERA-40 precipitation dataset from the National Center for Atmospheric Research for its long span (from 1957 to 2002), its four-times-a-day data points, and its agreement with observational data from the test period.

N Voisin, AW Wood, and DP Lettenmaier, “Evaluation of Precipitation Products for Global Hydrological Prediction,” Journal of Hydrometeorology, June 2008 (vol. 9, no. 3, pp. 388-346).

And Not a Drop to Drink

Historically, planners have confidently relied upon fall rains and spring snow melts to quench the thirst of towns like Seattle. But climate change means the old assumptions no longer apply. 3TIER’s Matt Wiley and the University of Washington’s Richard Palmer modeled the Cedar and South Fork Tolt river basins (Seattle’s main sources of water) in three steps: 1. With general circulation models to portray future climate; 2. With hydrologic models of each basin; and 3. With simulations of municipal water use.

Because of decreased precipitation and earlier snow melts, the authors predict that the summer and fall stream flows slaking Seattle’s thirst will be reduced by an average of 6 percent per decade. The snow pack feeding Seattle’s water supply will be reduced by an average of 15 percent per decade at the same time that its peak shifts to earlier in the year. By 2040, the winter snow pack above Seattle will be reduced by 50 percent. Finally, the authors predict that the amount of fresh water stored in Seattle’s drinking water reservoirs at the end of an average summer will decline by 1.9 percent per decade. Ultimately, that means Seattle’s reservoirs will yield 6.1 million gallons of water per day less each decade.

So what’s the good news? The article by Wiley and Palmer presents methods that can be used to model water availability and resource implications throughout the western United States.

MW Wiley and RN Palmer, “Estimating the Impacts and Uncertainty of Climate Change on a Municipal Water Supply System,” Journal of Water Resources Planning and Management, May/June 2008 (vol. 134, no. 3, pp. 239-246).