Geology topics

C.A. Aldridge

Publications and source records attributed to C.A. Aldridge.

3 recordsLinked to original sources

USGS2022

Reservoir attributes display cascading spatial patterns along river basins

Considering reservoirs as linear fragments in a basin's river network could improve understanding, predictability, and management efficiency. We looked for general cascading spatial patterns across five categories of reservoir attributes: land cover, morphology and hydrology, fish habitat, fish assemblages, and fisheries. Attributes were pulled from various databases for large reservoirs (>100 ha) located in the United States. 16 widely distributed river basins, each including a minimum of 15 large reservoirs, were selected for analysis. Using analysis of covariance with basin as the class variable, we tested each attribute as a linear function of catchment area, which is an index of reservoir position in the basin. The majority of reservoir attributes displayed log-linear patterns as catchment area increased, indicating that reservoirs act as members of a larger network just as river reaches do. Several patterns were detected including attributes with no apparent lengthwise arrangement along the basin; cascading spatial patterns in which attributes increase or decrease from upstream to downstream within a basin; and attributes that increase with catchment area in some basins, decrease in others, or may simply remain constant throughout the basin. We conclude that each pattern may have different implications for management, and that the effectiveness with which most management activities influence reservoirs is likely to increase or decrease along river basins.

Water Resources Research↗

USGS2021

Retention and dimensional changes of evergreen brush piles within a flood control reservoir

Brush piles (i.e., trees and large woody debris) are often installed in reservoirs to supplement fish habitat. The retention and dimensional change of brush piles after installation is important information that can be used to maximize the effectiveness of this management action. We evaluated the retention and dimensional change of 70 eastern red cedar Juniperus virginiana and bald cypress Taxodium distichum brush piles in an embayment of a drawdown reservoir up to four annual cycles of submergence and exposure. We used satellite imagery to supplement our onsite measurements of retention. We also examined spatial patterns of brush pile retention and dimensional change. Brush piles were lost at 10% per year, and their volume was lost at 14% per year. We compared our rates of brush pile retention and dimensional change with those from a holdout data set of 50 brush piles. Estimates between data sets did not differ statistically. Spatial patterns of retention and dimensional change coincided with morphological features in our study area, suggesting that retention and dimensional change is influenced by variable physical forces (e.g., wave action and flow) at installation locations. Our estimates of brush pile retention and dimensional change can be used to generally sustain desirable brush densities. For example, to maintain a fixed total volume of brush in our study embayment, roughly 23% of the total brush volume installed would need to be replaced annually. Similar research in reservoirs managed for other purposes is needed, as length and cycle of inundation could lead to variable rates of retention and dimensional change. Additionally, advancements into computer-assisted detection and volume estimation could reduce the time and effort needed to monitor brush piles.

Mississippi↗

USGS2020

Themes of contemporary inland fisheries goals

Goals are important for the effective execution of public trust responsibilities by state inland fisheries bureaus, but formulating meaningful goals is not simple. Often bureaus look to their past and to their sister bureaus in neighboring states when crafting goals for their own freshwater resources. Herein, we review the goal themes of fisheries bureaus using publicly available documents and guided by previous literature. We test whether goals exhibit geographic patterns presuming that differences and similarities in climate, natural resources, and people determine, to various degrees, the goal themes across the U.S. We identified nine distinct goal themes but found that they do not form clear geographic patterns, which contrasts with a similar analysis conducted in the 1970s. Since the 1970s, fisheries bureau goals have expanded and regionalism in goals has vanished. We suggest that changes in perspectives and communication technology, as well as provisions within nationwide funding mechanisms have led to goals becoming more homogenous across the U.S. and more diverse within each bureau.

Fisheries Magazine↗