Runoff Volume Prediction From Daily Climatic Data

Abstract

A two-soil-moisture-reservoir model is developed to improve the estimate accuracy of g runoff-volume-prediction model. Soil moisture accounting in the two reservoirs is an intermediate step to runoff prediction. A decay-type function describes the moisture depletion between days of rainfall. The moisture depletion constant in the function varies by season with soil moisture, pan evaporation, and mean daily temperature. The runoff-prediction equation relates runoff to rainfall and soil moisture at the beginning of the storm. Computed runoff volumes are compared with values observed on a 3-acre native grass-meadow watershed for an 11-year period. Accumulated computed amounts for the period agree within 1% of the accumulated observed amounts. INTRODUCTION Prediction of surface runoff volumes fromungaged watersheds is a major concern to hydrologists. Several methods and techniques for estimating storm runoff have been published. Among these is a runoff volume prediction method developed by Hartman et al. [1960] for the heavy clay soils in the Blacklands of Texas. The purpose of this paper is to present a refined model of this method, which uses two moisture reservoirs instead of one. Climatic, runoff, and soil moisture data from the Blacklands Experimental Watershed near Riesel, Texas, were used in developing the prediction model. Results of a test of the model are given for g native grass-meadow watershed. PREVIOUS WORK Numerous models have been developed to predict surface runoff [Chow, 1964; Committee for Hydrological Research, 1966]. Schulze [Committee •or Hydrological Research, 1966] started with the simple soil moisture bookkeeping method and worked up to the more sophisticated models. He noted the principal feature Copyright • 1969 by the American Geophysical Union. 84 for each model and pointed out the limitations that necessitated improved models. The present stage of development includes two-level and multicapacity accounting models. The two-level and multicapacity models take into account the complex effects of soils. In these models, the soil mantle is divided into layers, and each layer is represented by a reservoir. Hamon [1964] used two layers: one the active root zone of most rapidly changing moisture and the other a lower zone that contributed some moisture to evapotranspiration. However, most of the multireservoir models consider only one reservoir operative at any one time. That is, the first is completely filled or entirely empty before the second is operative, or vice versa. Yet, under field conditions, unsaturated flow and capillary moisture movement take place, and there can be exchange between reservoirs without requiring saturated flow. Reservoir simulation largely neglected land use. Land use, used herein to mean crop, affects lhe rate of moisture depletion. Hartman [1960], Hartman e• al. [1960], and Richardson [1966] recognized potential differences due to land use and developed moisture-depletion equations based on land use and season. Hartman et al.

Modeling groundwater recharge and flow in an upland fractured bedrock aquifer

“…Recharge of bedrock groundwater is controlled in part by the permeability of covering soils and sur®cial deposits, and in part by the transpiration eects of trees and other vegetation. These mechanisms may vary substantially with seasonal changes and with elevation in a steep alpine environment (McGuinness and Harrold 1962;Knisel, Baird and Hartman 1969;Parmele 1972;Woolhiser 1973;Saxton and McGuinness 1982).It was the objective of our study to characterize bedrock recharge and ow mechanisms in the 10.5 km 2 uppermost watershed of the Browns River in northwestern Vermont. In the study area (Figure 1), precipitation increases with elevation.…”

Runoff losses of cyanazine and metolachlor: effects of soil type and precipitation timing

“…This is important because total pesticide loss depends on the time lapse between rainfall inception and runoff initiation (Wauchope et al 1990). Antecedent soil moisture has the potential to increase runoff volume and reduce time to runoff (Barnett et al 1967;Knisel and Baird 1969).…”

Watershed evapotranspiration by the combination method

“…McGuinness and Harrold (1962) found that small-area streamflow at Coschocton, Ohio was regulated primarily by seasonal ET. Knisel and Baird (1969) found they could accurately predict runoff from a 3-acre watershed near Riesel, Texas by using a procedure which predicted soil moisture from ET-related variables,…”