Point cumulative semivariogram of areal precipitation in mountainous regions

Abstract Assessments of average annual precipitation (AAP) are necessary for hydrological studies of a watershed for various water resources activities. Although AAP isohyetal maps provide global information, the behavior of precipitation occurrence at and around any individual station cannot be assessed from such maps. For this purpose, the point cumulative semivariogram (PCSV) concept is presented and applied to precipitation records from Yucca Mountain, NV, USA. These PCSVs provide qualitative interpretations that are subsequently convertible to simple quantitative relationships for predictions. Further, PCSV provides information about the nugget effect, radius of influence, structural changes etc. within the regional variations in the precipitation event around each station. The application revealed that Yucca Mountain annual precipitation amounts are not regionally homogeneous but have three distinctive types of homogeneity subregions. In the first category there is no nugget effect in the regional precipitation around the site concerned whereas there is significant regional dependence at small distances from the site. The second category includes a rather perfect regional relationship around the station concerned up to a certain distance and then onwards there is an abrupt region of independence. Finally, the last category implies that the precipitation amount at a station accumulates due to local convective rainfall events.