World Reservoirs: Analysis of Quantitative Characteristics and Their Effect on the Structure of Long-Term Runoff Variations of Regulated Rivers

Data on 388 world reservoirs and changes in the annual, maximal, and minimal runoff in the rivers they regulate at the same number of gages have been generalized over 102 items for each series. The existence of reservoirs has been shown to cause, on the average, an increase in the coefficients of variation and asymmetry for long-term variations of river runoff along with an increase in the correlation between the annual (this is not true for the annual runoff of the rivers that are regulated by HPP reservoirs), maximal, and mi-nimal runoff of successive years, the orders of autoregression runoff models, and the share of runoff series that are nonstationary in terms of expectation. The effect of the regulating capacity of reservoirs (“regulation degree”) on the characteristics of long-term runoff variations has been analyzed. The subtler structure of long-term runoff variations of regulated rivers have been studied to identify the effect of “intermittent nonstationarity”—a runoff series of a regulated river can contain alternating segments corresponding to fragments of realizations of random processes with statistically significant positive and negative trends or with no trends. It is hypothesized that the construction of reservoirs causes a spontaneous increase in the intermittent nonstationarity in the variations of river water abundance.