Evapotranspiration by woody phreatophytes in the Humboldt River valley near Winnemucca, Nevada, with a section on soil-moisture determinations

__________________________________________ Dl Introduction.______________________________________ 1 Purpose and scope._____________________________ 2 Acknowledgments_ _ ___________________________ 2 Climate._______________________________________ 2 Species of woody phreatophytes__________________ 3 Winnemucca test site..__________________________ 3 Weather station._______________________________ 3 Evapotranspiration studies_________________________ 3 Definition of evapotranspiration__________________ 3 Evapotranspiration tanks.-______________________ 4 Construction of evapotranspiration tanks. ______ 4 Water-supply system..______________________ 5 Transplanting, survival, and growth of woody phreatophytes. _______________________________ 7 Operation of the tanks. _ _________________________ 8 Water levels______________________________ 9 Sources of water for evapotranspiration__________ 9 Rainfall.-_-_-__-----____-_________________ 10 Water supplied to the tanks..________________ 10 Soil moisture.______________________________ 10 Computations of evapotranspiration.._____________ 11 Plant growth and development-__________________ 11 Foliage volume.____________________________ 12 Problems._________________________________________ 16 Damage by webbing insects._____________________ 16 Damage by rabbits.____________________________ 17 Page Problems Continued Salt content of the soils.________________________ D17 Boron toxicity..______-__--______-----__-___ 17 Source and accumulation of boron in the top soil19 Leaching as a corrective measure-_________________ 22 Factors influencing evapotranspiration rates__________ 24 Expression of evapotranspiration losses and extrapolation to growth areas ______________________ 26 Arealmethod._____________________________ 27 Volume-of-foliage method-___________________ 27 Results of evapotranspiration studies __________ 27 Greasewood__ _ _____________________________ 27 Rabbitbrush____.___----------------------29 Willow--_-_-_----------------------------_ 30 Wildrose.______________________________ 30 Bare soil________________-_____-_--_-___-31 Summary. ______________________________--------_-31 Soil-moisture determinations, by A. O. Waananen __ 32 Soil-moisture observations at the Winnemucca test site_________________________________ 32 Equipment and procedure__________________ 32 Water contents observed___-______--_-------34 Water-content variations in 1963____________ 35 Water-content changes in shallow flood-plain deposits _____________-_-______--__--___-----_ 35 References. ______________________-___-__----------_ 41