Michael G. Ferrick

A model for vertical frazil distribution

A model is presented for the evolution of frazil over depth and with time in a turbulent flow. The net upward migration due to buoyancy of the frazil is opposed by intermittent mixing induced by large energy-containing eddies. A surface renewal model is used to describe the effects of large eddy mixing. Parameters that represent an entire water body are obtained by averaging those of discrete water columns using a probability density function. These parameters include the concentration profile, the surface age, and the surface layer thickness. A dimensionless surface renewal frequency characterizes the frazil distribution at equilibrium. The rate of heat loss from the water surface, the surface renewal frequency, and the critical surface layer thickness determine whether the frazil will evolve toward a well-mixed equilibrium state or a layered state. The model provides a physical basis for understanding the transition between these states, consistent with existing empirical criteria and field data.

Two communities join forces to study ice‐covered rivers and lakes

Lake and river ice are important hydrologic variables that increase in significance with latitude and elevation and produce a diverse array of impacts on physical, chemical, and ecological processes in lentic and lotic systems. For instance, ice jam or ice dam events in rivers impede flow and cause rapid and severe flooding upstream and low flow downstream. Such events produce flow magnitudes that mimic the annual extremes of flood and drought. Sequential flow extremes, where “drought” conditions are followed immediately by flooding, are unique to ice jam and release events. These dynamic flow conditions have important implications for erosion, transport, and deposition of sediment; movement of nutrients and contaminants; and quality of stream habitat. Ice jam processes depend on ice cover characteristics and stream flow, both of which are influenced by and sensitive to climate variability

Analysis of the Winter Low-Flow Balance of the Semiarid White River, Nebraska and South Dakota

Low-flow studies are needed to quantify the effects of water consumption on streamflow, water quality, groundwater resources, and contaminant transport. The low-flow water balance of a river in a cold region is simplified in winter because evapotranspiration is negligible, irrigation water withdrawals and diversions are halted, and precipitation occurs largely as snow, minimizing the spatial and temporal variability of runoff. We investigated the monthly low-flow water balance of White River reaches over seven consecutive winters. Water going into or out of storage as ice or melt, obtained with an air temperature index model, can be a dominant component of the water balance. The point estimate method is used to account for parameter uncertainty and variability, providing the mean, variance, and limits of dependent variables such as water storage as ice and inflow from a subbasin. Negative surface water yield from several-thousand- square-kilometer subbasins occurred regularly through the period, indicating a significant flow from the river to the alluvial aquifers. The winter water balance results suggest either a perched river or a coupled surface water-groundwater hydrologic system in particular subbasins, consistent with the field investigations of Rothrock (1942). The winter flow exchange between the surface and subsurface can be used to estimate the annual exchange for both hydrologic conditions.