Richard H. French

Lake modeling: State of the art

The state of the art of lake modeling is examined from the separate but complementary viewpoint of coupled, dynamic hydrodynamic/water quality models and semi‐empirical, steady‐state models for phosphorous and chlorophyll. With respect to dynamic lake models both one and two dimensional models are examined. Special attention is given to: (1) the techniques used to simulate mass and momentum transport; (2) the selection of appropriate hydrodynamic, biologic, and chemical model coefficients; and (3) new developments regarding the release of phosphorous from lake bottom sediments. With respect to the semi‐empirical steady‐state models, several phosphorous mass balance and several chlorophyll prediction models are considered. It is emphasized that these two types of models, if used properly, are complementary in addressing the problem of lake water quality.

Evaluation of Recharge Potential at Crater U5a (WISHBONE)

Radionuclides are present both below and above the water table at the Nevada Test Site (NTS), as the result of underground nuclear testing. Mobilization and transport of radionuclides from the vadose zone is a complex process that is influenced by the solubility and sorption characteristics of the individual radionuclides, as well as the soil water flux. On the NTS, subsidence craters resulting from testing underground nuclear weapons are numerous, and many intercept surface water flows. Because craters collect surface water above the sub-surface point of device detonation, these craters may provide a mechanism for surface water to recharge the groundwater aquifer system underlying the NTS. Given this situation, there is a potential for the captured water to introduce contaminants into the groundwater system. Crater U5a (WISHBONE), located in Frenchman Flat, was selected for study because of its potentially large drainage area, and significant erosional features, which suggested that it has captured more runoff than other craters in the Frenchman Flat area. Recharge conditions were studied in subsidence crater U5a by first drilling boreholes and analyzing the collected soil cores to determine the soil properties and moisture conditions. This information, coupled with a 32-year precipitation record, was used to conduct surface and vaodse zone modeling. Surface water modeling predicted that approximately 13 ponding events had occurred during the life of the crater. Vadose zone modeling indicated that since the craters formation approximately 5,900 m3 of water were captured by the crater. Of this total, approximately 5,200 m3 of potential recahrge may have occurred, and the best estimates of annual average potential recharge rates lie between 36 and 188 cm of water per year. The term potential is used here to indicate that the water is not technically recharged because it has not yet reached the water table.

Responses of plankton and nutrients to methylene blue-photosensitized lake restoration

Abstract Sections of eutrophic Lahontan Reservoir, Nevada were isolated using in situ microcosms and treated with 1.0 mg/L methylene blue to assess its effectiveness for lake restoration. Green algae (Chlorophyta) and diatom (Baciliariophyceae) levels decreased significantly within one day of treatment; however, blue-green algae (Cyanophyta) levels did not decline. Nitrogen and phosphorus concentrations did not increase after photochemical treatment over the 10-day study period.

Flood Hazard Assessment on Alluvial Fans: An Examination of the Methodology

The recognition and assessment of the hazard that flash floods can pose to structures located on alluvial fans is seriously deficient relative to the ability of the engineer to assess flood risk to structures located in the vicinity of perennial rivers. With the development of major urban areas and hazardous, radioactive, and mixed waste sites on alluvial fans in the southwestern United States, there is both an increasing need and interest in developing rational and reliable techniques for assessing the hazards floods pose to these developments and facilities.