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Norman Gustaf Benson

Publications and source records attributed to Norman Gustaf Benson.

7 recordsLinked to original sources
USGS1981

The freshwater‐inflow‐to‐estuaries issue

Over 55% of the United States commercial fish and shellfish catch is dependent upon estuaries for spawning and nursery functions, but estuaries cannot function ecologically without an adequate supply, seasonal inflow, and quality of freshwater from inland rivers. Such inland river development projects as constructing reservoirs, leveeing rivers, dredging navigation channels, and diverting water for agriculture, cities, and industry have drastically changed freshwater inflows to many estuaries on the Atlantic and Pacific coasts and the Gulf of Mexico. The problems on the Atlantic coast are primarily reduced water quality and increased rate of runoff although reductions in quantity appear to be developing. On the Gulf of Mexico decreases in freshwater inflow quantity have reduced estuarine production on the Florida and Texas coasts. On the highly productive Mississippi Delta, levee and navigation channel construction has diverted river inflow to the Gulf of Mexico rather than allowing overflow to the estuarine habitats; this has resulted in saltwater intrusion and marsh erosion. On the Pacific coast, inflow to the San Francisco Bay complex has been reduced by over 50%, resulting in drastic estuarine changes. Studies on freshwater inflow are underway in Chesapeake Bay, Louisiana, Texas, and the San Francisco Bay complex. The freshwater‐inflow‐to‐estuary problem can be addressed by (1) considering the ecological effects of proposed inland water projects on estuarine production and communities; (2) developing nationwide criteria for evaluating the freshwater needs of estuaries; (3) refining methods for defining the economic and noneconomic benefit of freshwater inflow to estuaries; and (4) using existing laws and directives more effectively.

Fisheries↗
USGS1980

Effects of post-impoundment shore modifications on fish populations in Missouri River reservoirs

In the Missouri River main stem reservoirs in Montana, North Dakota, and South Dakota, hydrodynamic processes have decreased the lengths of shorelines and changed their configuration during the first 20 to 25 years of impoundment. Shale shores of Lakes Fort Peck, Oahe, Sharpe, and Francis Case were rapidly eroded by wave action and water level fluctuation. Banks slumped, embayments filled, and stumps and debris were covered by sediment. Shale shores developed mean slopes of 5-7% in sections of reservoirs with 10- to 25-km fetches and more than 10% in sections with 3- to 7-km fetches. Glacial till tended to armor the shorelines and deter their degradation in all reservoirs. Bank-cutting was particularly severe up to 1973 in the readily erodible Fort Union sediments along Lake Sakakawea. Water level fluctuation retarded the development of stable shores. Some aquatic vegetation developed along shorelines and in shallow sections of reservoirs in which water levels fluctuated little. Substrate suitable for terrestrial vegetation did not develop along the shores of fluctuating reservoirs, except where alluvial deposits were present. Physical changes of the shore probably influenced fish abundance and species composition primarily by changing the quality and quantity of spawning and nursery habitat. Species that appeared to be adversely affected by shore changes required protected embayments or flooded vegetation for reporduction: white crappie, Pomoxis annularis : black crappie, P. nigromaculatus : yellow perch, Perca flavescens : northern pike, Esox lucius : bigmouth buffalo, Ictiobus cyprinellus : small mouth buffalo, I. bubalus : and carp, Cyprinus carpio . Fish that spawn in tributaries or on rocky shores were not greatly influenced by shore changes (although the growth rate of several species were slowed): sauger, Sander canadensis : channel catfish, Ictalurus punctatus : white bass, Morone chrysops : goldeye, Hiodon alosoides : and river carpsucker, Carpiodes carpio . One species, the walleye, Stizostedion v. vitreum , appeared to be benefited from the shore changes. Physical changes along shores have not been adequately addressed in reservoir ecological planning. Fish population data collected before reservoir shores have reached a reasonable degree of stability do not provide a reliable estimate of the ultimate species composition in a reservoir.

Montana, Nebraska, North Dakota, South Dakota↗