FUTURE NEEDS FOR DEVELOPMENT 233 



applying them to specific problems. Of themselves the basic 

 data are only a list of figures pertaining to a specific sampling 

 point. With an adequate foundation of the governing princi- 

 ples and the hydrologic characteristics of the area in which the 

 records were collected, an exhaustive analysis can lead to a 

 determination of the volume of water in a particular phase of 

 the hydrologic cycle within a specified area, provided that the 

 basic data are truly representative. Much can be done with 

 existing records, as shown by the Weather Bureau's scientific 

 analysis of normal precipitation in western Colorado, result- 

 ing in totals 30 per cent greater than computed by arithmet- 

 ical averages of the same records. 2 In general the "exhaustive 

 analysis" and scientific interpretation lag far behind the col- 

 lection of the basic data for all phases of the hydrologic cycle. 

 The recommendations made to the Hydrologic Subcom- 

 mittee of the FIARBC for collection of basic data included 

 very little pertaining to infiltration, soil moisture, ground 

 water, and evapotranspiration — the underground phases of 

 the hydrologic cycle. So little is known about these phases that 

 even the listing of the national needs for additional data is a 

 formidable task. Instruments have not been perfected for 

 measurement of the water in some phases: equipment for 

 measuring soil moisture has recently been designed and is still 

 being tested under field conditions, 3 and measurement of 

 evaporation and transpiration is a matter for further research 

 and development. Also, it is exceedingly difficult to select 

 sampling points representative of any area of appreciable size, 

 because of the great variability in conditions under which 

 water moves downward from the land surface, laterally, and 

 then to the surface again. The records from these sampling 

 points are not of full value until they can be translated into 

 volumes of water within a particular phase of the hydrologic 

 cycle. In particular, an adequate continuing inventory of the 



2 Bernard, Merrill, The Role of Hydrometeorology in Planning the Water 

 Economy of the West, Trans. Am. Geophys. Union, vol. 30, pp. 263-271, 1949. 



3 Colman, E. A., The Place of Electrical Soil-moisture Meters in Hydrologic 

 Research, Trans. Am. Geophys. Union, vol. 27, pp. 847-853, 1946. 



