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== Photograph ==
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Heggie Nordahl (H. N.) Holtan

== Dates ==
10.0.4.1909 (Stoughton, WI, USA) - 20.3.2006 (Vero Beach FL, USA)

== Biography ==
Heggie (H.N.) Holtan,, the youngest of 13 children of a large Norwegian farm family. Although initially trained to teach physical education, he pursued an engineering career in hydrology. He championed the creation of the Hydrograph Laboratory at the National Agricultural Research Center to collect and correlate field data from all over the United States into a central database, and he developed an infiltration equation that predicted rainfall absorption and flood runoff for various soils and terrains. He remained as director of the lab until his retirement in 1974 after 42 years of service. He published many research papers, and was invited to speak at conferences all over the world. He was a founding member of Holy Trinity Lutheran Church in Laurel, MD. In 1981 he moved to Vero Beach, where he gave generously of his time and talents to many volunteer projects. 

== Hydrological Achievements ==

As well as leading the USDA Hydrology Laboratory, Holtan made significant contributions to the infiltration theory concept of runoff generation (including being amongst the first to use a time compression assumption), to establishing good practice in hydrological observations (Holtan et al., 1962) and to the early days of hydrological modelling (Holtan and Overton, 1964; Holtan and Lopez, 1971).  He introduced an infltration equation in that was one of the first to make infiltration capacity dependant on storage capacity and cumulative nifdltration (Holtan, 1961)  He was instrumental in establishing a USDA database of many thousands of soil hydrological characteristics (Holtan et al., 1968) that was later used in many studies of peso-transfer functions.

== Anecdotes ==

== Reference Material ==

== Selected Publications ==

Sharp, A.L. and Holtan, H.N., 1940. A graphical method of analysis of sprinkled‐plat hydrographs. Eos, Transactions American Geophysical Union, 21(2), pp.558-570.

Sharp, A.L. and Holtan, H.N., 1942. Extension of graphic methods of analysis of sprinkled‐plots hydrographs to the analysis of hydrographs of control‐plots Small Homogeneous watersheds. Eos, Transactions American Geophysical Union, 23(2), pp.578-593.

Holtan, H.N., 1945. Time‐condensation in hydrograph‐analysis. Eos, Transactions American Geophysical Union, 26(3), pp.407-413.

Holtan, H.N. and Kirkpatrick Jr, M.H., 1950. Rainfall, infiltration, and hydraulics of flow in runoff computation. Eos, Transactions American Geophysical Union, 31(5), pp.771-779.

Holtan, 1961. A concept for infiltration estimates in watershed engineering. USDA, Agricultural Research Service Publication 41-51.

Holtan, H.N., Minshall, N.E. and Harrold, L.L., 1962. Field manual for research in agricultural hydrology (No. 224). Soil and Water Conservation Research Division, Agricultural Research Service.

Holtan, H.N. and Overton, D.E., 1963. Analyses and application of simple hydrographs. Journal of Hydrology, 1(3), pp.250-264.

Holtan, H.N. and Overton, D.E., 1964. Numerical experiments in generating and routing watershed runoff. Transactions of the ASAE, 7(4), pp.402-0408.

Holtan, H.N. and Overton, D.E., 1965. Storage-flow hysteresis in hydrograph synthesis. Journal of Hydrology, 2(4), pp.309-323.

Holtan, H. N. and N. R. Creitz. 1967. Influence of soils, vegetation and geomorphology on elements of the flood hydrograph. Symposium on floods and their computation, Leningrad, Russia.

Holtan, H.N., England, C.B. and Shanholtz, V.O., 1967. Concepts in hydrologic soil grouping. Transactions of the ASAE, 10(3), pp.407-0410.

Holtan, H.N., England, C.B. and Whelan, D.E., 1967. Hydrologic characteristics of soil types. Journal of the Irrigation and Drainage Division, 93(3), pp.33-42.

Holtan, H.N. et al., 1968. Moisture-tension data for selected soils on experimental watersheds (Vol. 41). Agricultural Research Service, US Department of Agriculture.

England, C.B. and Holtan, H.N., 1969. Geomorphic grouping of soils in watershed engineering. Journal of Hydrology, 7(2), pp.217-225.

Holtan, H.N. and Lopez, N.C., 1971. USDAHL-70 model of watershed hydrology (No. 1435). US Department of Agriculture.

Frere, M.H., Onstȧd, C.A. and Holtan, H.N., 1975. ACTMO, an agricultural chemical transport model (Vol. 3). Agricultural Research Service, US Department of Agriculture.

Holtan, H.N., 1975. USDAHL-74 Revised model of watershed hydrology: A United States contribution to the international hydrological decade (No. 4). Agricultural Research Service, US Department of Agriculture.

Fisher, G.T., Ayars, J.E., Holtan, H.N. and Nelson, D.L., 1979. USDAHL-74 model as a planning tool. Transactions of the ASAE, 22(6), pp.1347-1352.

== Links ==

[[Category:Biographies of Hydrologists]]