Posted on August 1st, 2017

Our Changing Landscape – Twitchell Reservoir, California

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 10 billion square kilometers of data. In July, we looked at the amazing California super bloom that occurred this Spring after the torrential seasonal downpours; and this month we continue the focus on California with a look at Twitchell Reservoir and its rapid refill this year after the abundant rain.

The RapidEye Constellation

Click on the image above to see an animation of 5-meter natural color RapidEye imagery collected over Twitchell Reservoir on July 4, 2010, September 20, 2016, January 16, 2017 and May 16, 2017. In the 2016 to 2017 images, you can see just how quickly the reservoir levels recovered after being essentially dry in the September 2016 data – amazing! The July 2010 RapidEye image was added just to give context and show that variation in the level of Twitchell Reservoir is not new – even if it was pronouncedly dramatic in the historic Californian droughts of the past few years. (Images Courtesy: Planet @ 2017)

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.

The Refill of Twitchell Reservoir, California

As we mentioned last month, in some parts of California, they have received months’ worth of rain in just a few short weeks. This plethora of rain had a dramatic impact on the state’s reservoir system – many of which were nearly empty. We have covered the depletion of California’s reservoirs in past Our Changing Landscape, for example Folsom Lake in our July 2014 edition; and this month we are happy to cover the opposite, the refilling of Twitchell Reservoir. If you would like to see low resolution imagery of many of California’s reservoirs before and after the Spring rains, here is an excellent article to check out.

Twitchell Reservoir spans the borders of Santa Barbara County and San Luis Obispo County. Constructed in the late 1950s, the human-made lake supplies water and flood protection to the Santa Maria Valley. Twitchell has a capacity of 194,971 acre feet with a maximum water elevation of 651.5 feet (198.6 meters). In late January 2017, Twitchell stood at just 5.5% of its capacity; and after the rains of Spring 2017, the reservoir rebounded significantly to 37.3% of its capacity as of late June where the County of Santa Barbara received 136% of its normal-to-date rainfall. Now it is time to turn to the 5-meter RapidEye archive to see just how much of the lake has returned!

If you would like to find out more about using RapidEye for your academic studies, engineering projects or any landscape analysis, let us know at sales@apollomapping.com or (303) 993-3863.

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