In this monthly feature, we span the globe to examine Our Changing Landscape with time series of medium resolution RapidEye satellite imagery. The RapidEye archive dates back to late 2008 and already contains more than 5 billion square kilometers of data. This month, we look at the impact of the historic California drought one of its many reservoirs, Folsom Lake.
The RapidEye Constellation
RapidEye is a constellation of five 5-meter medium resolution satellites each offering five spectral bands of information. The RapidEye constellation offers daily revisits to every location on the planet with a huge footprint that is 77-km wide. The data is priced competitively with a starting cost of $1.28 per square kilometer for all five spectral bands – academics do receive discounts. RapidEye adds a fifth band, the red edge, to the ‘traditional’ multispectral set of blue, green, red and near-infrared (NIR). The additional spectral data in the red edge band allows users to extract more useful land ‘information’ than can be from traditional 4-band imagery sources. When RapidEye imagery is ordered as a Level 3A Orthorectified product, images from multiple dates are extremely well registered, making it the ideal data source for Our Changing Landscape.
California Droughts – Folsom Lake
I am guessing that it comes as no shock to many of our readers when I make the statement that California is in the midst of a historic drought. In fact, during 2013, the state received less rain than any year since record keeping started in 1895; and if the recent climatic trends continue, 2014 will likely be even drier. And whether you believe in anthropogenic climate change or not, a recent study by Simon Wang, Assistant Professor of Climate at Utah State University, has linked the impacts of this phenomena to the ongoing California droughts. Specifically, the study suggests that unusually cold waters in Southeast Asia created a persistent high-pressure ridge to build up last year over the Gulf of Alaska which prevented normal levels of precipitation from flowing over the state. Thankfully, parts of California received heavy rainfall over the past few months, particularly during March, totaling 4 to 11 inches, however even this significant precipitation has done little to reverse the affects of the historic drought. Here are some frightening statistics on just how bad the drought in California is:
- On May 15th, the US Drought Monitor designated the entire state as having severe or worse drought; during the same time last year, only 46.25% of California was designated as such.
- Governor Jerry Brown signed a $687 million drought relief package in spring which included $21 million for drought-related unemployed workers and $25.3 million for food aid.
- California’s snowpack supplies about one-third of the state’s water needs. As of March, the statewide snowpack was about 20% of average; on April 1st, the figure was 32% of average; and by May 1st, the figure was just 18% of average.
- During February, 17 rural communities announced they were within 100 days of running out of water.
- The fire season in California is now 75 days longer than just a decade ago. This season started weeks before average with more than 30 fires burning up and down the state. As of May 15th, officials had already battled 1,440 wildfires, twice the average number by this time of the year.
Located at the base of the Sierra Mountains in northern California, Folsom Lake is about 25 miles northeast of Sacramento. Folsom Lake was created in 1955 when the Folsom Dam was built. The dam was designed to hold back 1.01 million acre feet of water which would cover an area of 11,450 acres. During normal seasons, lake levels fluctuate from 460 feet in late spring to less than 400 feet by late summer. Folsom Lake supplies water to some 265,000 residents of Citrus Heights, Fair Oaks, Folsom, Granite Bay, Orangevale and Roseville. As of February 4th, the reservoir held less than 17% of its capacity, revealing cultural sites once flooded by the lake’s waters that had not been seen in decades, if ever, since 1955. While the watershed surrounding Folsom Lake received rain during March and April, it currently stands at 56% of its capacity, far below its average this time of the year of 68%.
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