The daily rain, snow, or mixed‐rain‐and‐snow catch by five different rain‐gage installations was measured near Hastings, Nebraska, during the period January 1946 through September 1961. Rain‐gage installations included were a U.S. Weather Bureau standard 8‐inch gage, a weighing‐recording gage, a standard gage on a 6‐foot post, a standard gage equipped with an Alter shield, and a standard gage equipped with a Nipher shield. The shielded gages caught slightly more precipitation (significant at 1 per cent level) than the unshielded gages. When rainstorms were divided into 0.5‐inch increments, the performance of the five different rain gages was not consistent. Some of the differences were statistically significant. The differences in performance of the several gages were so small that they have no practical significance. True precipitation is unknown.
The data utilized in developing the following method of analyzing hydrographs of sprinkled plats was secured by an infiltration‐study party of the Office of Research of the Soil Conservation Service, under the supervision of G. W. Musgrave. The work was done on the Concho River Watershed, near San Angelo, in West Texas, during the summer and fall of 1939. The data used are those from Type‐F rainfall simulator‐plats. This infiltrometer is the latest development of the Hydraulic Laboratory of the Soil Conservation Service. Plats were six feet wide and 12 feet long.
One of the principal problems in hydrology regression problems in hydrology will show is to define the effects of changes in land use that they do not conform to a multivariate on the regi'men of streams. Because of the normal distribution. Such variables as water many factors affecting streamflow, the in-year, degree of urbanization, percentage of ability even to recognize some of them, and basin in row crops, and miles of terracing are the lack of precision in describing them quanti-not randomly distributed. For statistical retitively, streamflow must be expressed by a lations which include at least one variable statistical relation. Multiple regression is a of this type the correlation coefficient may not useful tool for this purpose provided that the give a valid measure of the relation between required assumptions can be met.
variables. Sharp, Gibbs, Owen, and Harris [1960]The distinctions between regression and recognized the weakness of the correlation correlation must be recognized in order to coefficient as an indicator of the quality of the successfully apply and interpret either of the estimating equation. Most texts on applied methods. These distinctions are very marked, statistics emphasize the correlation rather than although they may seem of little importance the regression model, and as a consequence because of the similarity of the computation hydrologists tend to evaluate results of reprocedures. In the case of linear correlation gression a•mlyses as if they were correlation the assumptions are made that the data are analyses. A recognition of the regression problem drawn from a bivariate or a multivariate normal is necessary before the appropriate interpretation distribution and that the observed values are of a specific analysis can be made.
The development of the plans of Infiltration Studies (under the direction of G. W. MUSGRAVE, Office of Research, Soil Conservation Service, United States Department of Agriculture, Washington, D.C., and with the cooperation of the Hydrologic Division, same office) to make simultaneous studies of small watersheds by means of infiltrometers and small control‐plots, and the watersheds as a whole, has made it desirable, even necessary, to develop more precise methods of analyzing hydrographs of such control‐plots and the small watersheds. Following is a proposed method of extending and adapting the graphic method of analyzing sprinkled‐plot hydrographs developed by the authors for this purpose [see 3 of “References” at end of paper].
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