Bishop, Gary D. and M. Robbins Church. 1998. Hydrologic Mapping. Encyclopedia of Hydrology and Water Resources pp 371-374, Encyclopedia of Earth Sciences Series, Kluwer Academic Publishers, Boston.
Mapping is a concise way to display and summarize the spatial distribution of hydrologic variables, such as the elements of the hydrologic balance (i.e., precipitation, evapotranspiration, and runoff). Hydrologic maps can be an effective communication tool for science, educational, and socio-political purposes and thus can play an important role in many of the environmental and social problems. Hydrologic maps are a relatively recent development (probably >150 years) and can take many forms (Mackay and Thomas, 1971, Robinson 1971). For gaged, measured, or estimated data having continuous scale of measurement the two most common types are 1) a point map, or 2) an isoline map when data are interpolated/extrapolated over the earths surface. This paper deals mainly with the second type of map, isoline maps.