Headwater streams are an integral part of the ecological health of the greater stream network as they provide valuable biological habitat, provide upwards to 95% of total in channel flow, while providing downstream reaches with important constituents such as sediment and woody debris. Small headwater streams are particularly susceptible to...
An experimental and numerical modeling investigation was conducted to study interactions between microbial dynamics and transport processes in variably saturated porous media. These interactions are important in a variety of applied problems such as water and wastewater treatment, bioremediation, and oil-field recovery operations. These processes and interactions also have great...
Vertisols and other vertic-intergrade soils are found all over the globe, including many agricultural and urban areas. These soils are characterized by their cyclical shrinking and swelling behaviors, where bulk density and porosity distribution both vary as functions of time and/or soil moisture. In turn, alterations in physical soil parameters...
Rainfall scarcity and variability present serious challenges to water security for many rural communities throughout the world's drylands. Sand dams--weirs built across ephemeral or seasonal rivers--provide an appropriate water harvesting and storage option for many regions. The structures quickly fill with sediment during rainy season flow events and store water...
Non-dilute salt strength solutions occur in many near surface geologic environments. In order to better understand the occurrence and movement of the water and salt, mathematical models for this non-ideal fluid need to be developed. Initial boundary value problems may then be solved to predict behavior for comparison with observations....
Linkages between land use and its influence on the atmosphere have been a long-standing research area. For example, what is the impact of irrigated agriculture on downwind rainfall? Global-scale models show that moisture recycling is an important source of water for inland regions around the world, but they do not...
Infiltration of highly concentrated solutions into unsaturated sand is suspected to be affected by the liquid-gas interfacial tension between the resident water and that of the infiltrating solution. The wetting of non-porous solid surfaces by liquids is commonly quantified by contact angle measurements. However, it is well known that wettability...
The City of Woodburn, Oregon's Wastewater Treatment Plant (WWTP) has been investigating several natural alternatives for improving effluent quality. Based on its current National Pollution Discharge Elimination System (NPDES) permit, the WWTP will require additional reduction of temperature and ammonia levels in the summer, especially in the critical month of...