Monitoring of the droughts consequence by high resolution satellite images
Authors: Mozgovoy D. K. 
Published: February 2018

The State of California is one of the least abundant with fresh water in the United States, while having high water consumption – the drought in the state has reached catastrophic proportions. January 2015 was the driest month in California for the whole period of observations since 1895. Two thirds of the state's population depend on the centralized water supply – about 25 million people and more than 400 thousand hectares of agricultural land. The level of ground waters and the snow cover have become record low – this can be explained by pumping groundwater out for irrigation of agricultural land. The water level in the reservoirs of California is close to the critical notch. State authorities are forced to tighten measures to save water, the supply of which is sometimes insufficient to satisfy the priority needs of citizens. The solution of the problem of rational use and protection of water resources can only be based on an integrated systemic approach to the study of spatial and temporal patterns of natural and anthropogenic factors on the quality and quantity of surface water with the use of satellite and ground data. In the study of the water regime of land one of the most important input parameters of hydrological models is the surface area of the reservoirs. Regular receiving of information about this parameter with the use of ground data is challenging and labor intensive. Using satellite data can greatly simplify this task and accomplish it with shorter latent periods, more frequently and at lower costs. The results of satellite monitoring of certain areas of California shown to assess the impact of the drought in 2011–2015 on the large freshwater bodies, based on high resolution satellite images. To quantify the effects of drought in 2011–2015 on selected large freshwater bodies (Lake Folsom and Lake Oroville) processing of multispectral images was performed. Changes of Lake Oroville in 2011–2015 according to high resolution satellite images was detected. The shift of the coastline near Foreman Creek amounted to 2.5 km. The shift of the coastline near Lampkin Road amounted to over 1.2 km. Changes of Lake Folsom in 2011–2015 according to the high resolution satellite images was detected. The shift of the coastline near the Beal's Point made 1.2 km. The shift of the coastline near Peninsula Campground made over 3.4 km. Large-scale consequences of drought shown for lakes Oroville and Folsom are also typical for other fresh water bodies of California, the majority of which have the status of water reservoirs, and also for water bodies of other US states. For instance, Lake Mead covering 90 % of water requirements of Las Vegas has the water level by 145 feet below normal. It is expected that this level will go down by another 20 feet by June, 2015. This is not only about water, but also about electricity supply – dams of hydropower plants are almost dry. Therefore, in the recent years an acute necessity has appeared for creation of a web-service for regular space monitoring of fresh water bodies – now this has become possible owing to availability of satellite images and modern technologies of their processing. The users of such a service may be: – state regulating structures (water supplying enterprises, forest, environment, agricultural services and so on); – state and private companies of water transport (unbiased evaluation of the consequences of the drought for fresh water navigation); – tourist companies (monitoring of recreational territories); – municipal services, private companies, farmers (carrying out measures for minimizing water consumption); – TV and radio companies and other mass media (propaganda of rational water use); – population living near territories affected by the drought (obtaining of unbiased and reliable information as for the scale and severity of the consequences of the drought).