Construction Of Small Dams Research Articles

The Effect of Regulation Caused by a Dam on the Distribution of the Functional Feeding Groups of the Benthos in the Sub Basin of the Grande River (San Luis, Argentina)

The construction of small dams in principal streams is one of the most common forms of regulation in the province of San Luis since they cause changes of physical, chemical and biological nature downstream. The purpose of this study was to analyze the short-term modifications in the food organization of benthic macroinvertebrates communities due to the construction of a dam in the Grande River (San Luis, Argentina). Two sampling sites were established: one before the dam and another one after it. The samplings were carried out with Surber sampler and during an annual cycle extending from April 1997 to March 1998, and two complementary samplings were done in low and high waters. The field sampling design was stratified randomly, and 3 pseudo replicas were taken in a transect seasonally and monthly and were then averaged. Macroinvertebrates were classified in different functional feeding groups. The comparisons at the level of physical and chemical variables and absolute abundances of the functional groups were carried out by means of the Wilcoxon test for two related samples. The collector-filterers, scrapers and predators increase whereas the collector-gatherers and shredders decreased. There were significant differences at the level of gatherers and shredders.

Threatened fishes of the world: Barbus haasi (Mertens 1925) (Cyprinidae)

barbel not reaching the rear edge of the eye. Last unbranched ray of the dorsal fin with small denticles. Anal fin is long and caudal peduncle is short and high. Body presents dark blotches. Part of caudal, anal and pelvic fins are red. Drawing by Rafael Miranda. Distribution: Most headwater streams of the Ebro River Basin and North Mediterranean rivers of the Iberian Peninsula. Abundance: Restricted to headwaters and occasionally in middle reaches of streams, scarce where present. Habitat and ecology: This benthonic species prefers upper reaches of rivers, with high flow and clear, cold waters. Barbus haasi occurs in rocky and vegetated areas and feeds on macroinvertebrates (mainly Chironomidae, Ephemeroptera and Trichoptera). Reproduction: The spawning period extends throughout April and June, related to periods of high stream flow. Fecundity ranges from 2000 to 7000 eggs per female. The males have an early maturity (one year) and grow more slowly than females. The females live for 8 years while the males only live for 7 years. The females have multiple spawning, releasing two to five egg batches depending on their size, such that largest females spawn more batches than the small ones (Aparicio & Sostoa 1998). Threats: The species is threatened by invasive alien fish species (mainly piscivores) and habitat loss due to water abstraction, construction of small dams, stream desiccation, etc. Anthropogenic water pollution is another important disturbance factor. This endemic species of the Iberian Peninsula is currently in rapid decline because the above noted impacts are intensified by the characteristic irregularity of the Mediterranean rivers. Conservation action: None. Conservation recommendations: Waste water and water pollution control and treatment. Correction of the impact of stream regulation by water releases to simulate natural flow patterns. Prevent alien fish species introductions and eradication of the existing alien species which impact on B. haasi. Habitat protection and control of invasive alien fish species are the main actions necessary to prevent the further decline of Barbus haasi. Remarks: There has been some controversy with regard to the systematic position of

Creation of Trout Habitat by Constructing Small Dams

The purpose of this study was to try to create a habitat suitable for trout by deepening the headwaters of Sagehen Creek through the construction of small dams 1 to 2 ft. in height. Located in the northeastern Sierra Nevada of California, this shallow section of Sagehen Creek contained no trout in July 1957 when work was begun. After the dams were built, wild brook trout, Salvelinus fontinalis (Mitchill), from a natural population lower in the creek were introduced into the headwaters.