Dendrohydrology provides accurate methods for studying long‐term hydrologic variability at regional scales. A substantial literature and body of knowledge exists, attesting to the value of tree ring based hydrologic reconstructions to discern patterns of long‐term hydrologic variability. Application studies encompass drought analysis, analysis of extremes, periodicity of rare hydrologic phenomena, regional interdependence of surface moisture conditions, and, in general, the probabilistic analysis of key hydroclimatic variables such as runoff, precipitation, and temperature. The probabilistic analysis includes distributional properties, frequency duration analysis, severity of events, and spatial variability of hydrologic indicators. This paper reviews some fundamental aspects of dendrohydrology, with a perspective on its value to hydrologists in pursuit of an understanding of long‐term hydrologic spatial‐temporal behavior and provides also a selective citation of previous work conducted within the dendrohydrologic discipline. Copyright 1993 by the American Geophysical Union.

Tree‐ring reconstructions of centuries‐long streamflows in four river basins of western United States were used to assess the severity, frequency and distribution of duration of droughts in the basins, and the probability of extreme drought in well‐populated areas of California and Arizona. Our results show (i) greater long‐drought threat than that inferred from historical streamflow records; (ii) weak statistical dependence of streamflows across the river basins; and (iii) significant probability of droughts in individual river basins. Copyright 1992 by the American Geophysical Union.