INFILTRATION EVALUATION OF FOUR MECHANICAL RAINFALL SIMULATION TECHNIQUES IN SIERRA NEVADA WATERSHEDS¹

Abstract

Little quantitative site‐specific infiltration, runoff and sediment transport data for Tahoe Basin soils under varying storm events or stage of development are available. Modular (Ml), F‐type (M2), Impact nozzle (M3), and Impact‐Fan nozzle (M4) rainfall simulators were evaluated as to their practicality and ability to characterize infiltration for the Cagwin Soil Series within the Tahoe Basin. Three slope (0–15,15–30, >30%) and four plot conditions (natural with duff [P1], natural without duff [P2], disturbed without duff [P3], and disturbed with duff [P4]) were studied. The measured data were incorporated into a modified Philip's infiltration model and multiple non‐linear regression analyses were used to examine relationships between method, slope, plot condition, and infiltration characteristics.t Simulation methods Ml and M4 produced statistically similar (P=0.01) infiltration data, as did M2 and M3 which produced lower infiltration rates. All were found suitable for use in Sierra Nevada watersheds. Ml was considered most practical. Slope had negligible effect on infiltration. The plot condition was found to significantly influence infiltration, and the effect of each plot condition was significantly different. Final infiltration rates ranged from 4.7 to 6.2 cm/hr. Thus, the Cagwin soil demonstrated moderate to high infiltration rates even when exposed to extreme storm conditions (8–10 cm/hr).

Lake Tahoe watershed assessment: volume I

“…A subsequent University of Nevada, Reno (UNR) study focused on sediment discharge from four different plot conditions on Meeks Creek (Naslas 1991). The conclusions were similar to those of Guerrant et al (1991) in that soil disturbance and slope were identified as the greatest predictors of sediment transport. The highest sediment came from the wooded disturbed site without duff, and the least from the wooded natural site with duff intact.…”

“…Sediment concentrations are lower downstream, suggesting a sediment trapping effect. Discussion of (Guerrant et al 1991;Naslas et al 1994). Land development and lack of revegetation also can be major factors in sediment loading.…”

“…Although this study demonstrated which site conditions (disturbed/undisturbed, duff/no duff) were more likely to erode, application to other Tahoe basin soil types of different erosivity classification cannot be directly inferred. Guerrant et al (1991) also noted that only interrill erosion was examined and not rill erosion, which may be a greater source of sediment discharge on some soils. A subsequent University of Nevada, Reno (UNR) study focused on sediment discharge from four different plot conditions on Meeks Creek (Naslas 1991).…”

“…Guerrant et al (1990Guerrant et al ( , 1991 evaluated the runoff and site-specific erosion potential of the Cagwin soil (common to the Tahoe basin). This work was intended to examine soil's ability to be infiltrated under conditions of excessive artificial precipitation.…”

A Synthesis of Sierran Forest Biomass Management Studies and Potential Effects on Water Quality

“…The specific sources of nutrient and sediment loading to Lake Tahoe, although varied, are generally related to anthropogenic enhanced atmospheric deposition, overland flow surface runoff, and/or subsurface transport and discharge. If we are to arrest continued deterioration of the lake's famed water clarity, it is imperative that in addition to the current emphasis on urban sources of water pollution we also strive to better understand the interdependence among watershed nutrient cycling, groundwater and streamflow, overland flow surface runoff, precipitation (type, intensity, duration), atmospheric deposition, wildfire and anthropogenic manipulations such as biomass management [11][12][13][14][15][16][17][18][19][20][21][22].…”