摘要:

AbstractThe Sungai Negara basin covers about 4000 km2of the Barito river floodplain in south‐east Borneo (Kalimantan). In view of plans to regulate the swamps in this area by impoldering or drainage a model study was initiated to describe the present state of the system and to assess potential impacts of these developments. In this paper a summary of the climatological, hydrological and topographical database is given, and model equations formulated. A comparison between calculated and observed river levels shows good agreement. The model is then used to estimate the increase in peak flows in the hypothetical absence of wetlands in the system. The results show that impoldering large areas of the wetlands would considerably increase the risk of flooding in the area. In another application, the model is used to calculate residence times in the lakes and swamps. This makes it possible to indicate the areas most sensitive for pollution. The results are also useful to assist in a soil mapping study, as only areas with very long residence times (only rain fed) coincide with peat area

ISSN:0886-9375    

DOI:10.1002/rrr.3450070402

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe invertebrate fauna of 10 river systems, five with impoundments and five without, were sampled. No significant difference was found either in taxonomic richness or invertebrate densities between impounded and unimpounded sites at similar positions along river continua. However, plecopteran species richness was significantly lower and plecopteran density reduced in post‐impoundment sites. Densities ofDeleatidiumspp. (Ephemeroptera: Leptephlebiidae) were significantly lower at lake outlets compared with other sites. Two species ofZelandobius(Plecoptera: Gripopterygidae) andEriopterini(Diptera: Tipulidae) snowed distributions apparently curtailed by impoundments, whereasPotamopyrgus antipodarum(Mollusca: Hydrobiidae) had an extended distribution. Margalef's, Menhinick's, Berger‐Parker and Shannon indices, total taxa present and plecopteran taxa were plotted against stream order, stream width and distance from the source. Menhinick's and Shannon‐Weaver indices produced statistically significant but weak regressions, and discontinuity distances and intensity could not be accurately calculated. The usefulness of diversity indices as a measure of the magnitude of impoundment effects in the South Island seems to be li

ISSN:0886-9375    

DOI:10.1002/rrr.3450070403

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractQuantitative and qualitative data on channel changes along the lower Vistula arising from regulation works carried out in the 19th and 20th centuries are presented. Channel width was reduced by 50% and the bed lowered by 1.3 m. Changes of the river's hydrodynamic conditions in the segment from Wloclawek to Swiecie during the last 140 years are discussed. Changes of the bed load balance are characterized.

ISSN:0886-9375    

DOI:10.1002/rrr.3450070404

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractDuring the last 20 years numerous water supply, hydroelectric and other large structures have been built along the Drava River and in its catchment area in Slovenia, Croatia, Hungary and Austria. Their construction has greatly influenced the water regime of the Drava River, especially during low water periods. The changes in the low flow regime along the stretch from Varazdin (285 km) to its confluence with the Danube (0 km) are examined. The analysis includes changes in the water levels, discharges and the amounts of suspended sediment and bed load. The intensity of changes, the time of their occurrence and their trends are examined.

ISSN:0886-9375    

DOI:10.1002/rrr.3450070405

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractSince its completion in 1973 the Danjiangkou Dam has markedly changed downstream flows, water levels, temperatures, sediment loads and other water quality characteristics in downstream reaches of the Hanjiang River. There have been changes in the growth, spawning behaviour and overwintering condition of local fish populations, in the composition and abundance of food organisms and in the composition of the commercial fish catch. Despite the changed environment and the absence of a fish pass, fish populations are still able to grow and spawn under the new regime. Where conditions are like those of the Hanjiang River, dams may not necessarily have calamitous consequences for fishery production.

ISSN:0886-9375    

DOI:10.1002/rrr.3450070406

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractHong Kong streams serve as indirect catchments for storage reservoirs to which they are connected by a network of undergound tunnels. Water transfer to reservoirs reduces stream flow downstream of the extraction point, and surface flows may disappear in affected reaches during the dry season. The ecological effects of periodic dewatering on aquatic insects were investigated in Tai Po Kau Forest Stream, Hong Kong, where water extraction at a weir gives rise to intermittent flow immediately downstream of a well studied perennial stream section. Benthic samples were taken from the intermittent reach on 48 occasions over a two year period encompassing two dry seasons. Trends in total population densities were unclear, with considerable fluctuations over the study period. In contrast, species richness declined markedly after surface flow disappeared, reaching the lowest values at the end of both dry seasons. A rapid increase accompanied flow resumption on the onset of the summer monsoon, and maximum wet season values were up to five times greater than species richness during the dry season. Dry season declines in Ephemeroptera and Trichoptera were accompanied by a dramatic increase in Coleoptera (Elmidae and especially Helodidae). The situation was reversed during the wet season when Trichoptera (especiallyCheumatopsycheandChimarra) and Ephemeroptera (Leptophlebiidae, Baetidae and Heptageniidae) were numerous. Community structure in the intermittent reach recovered quickly from the dewatering disturbance, due largely to recolonization by drifting animals. At the scale investigated, the community was resilient to disturbance because a source of mobile colonists was available upstream. However, if dewatering affects reaches far downstream, the presence of suitable colonists in upstream reaches cannot be guaranteed, and recovery from disturbance will be delayed. Lowland streams in Hong Kong are often polluted and host to exotic species; in such circumstances the effects of water transfers are exacerbated and recolonization is hindered.

ISSN:0886-9375    

DOI:10.1002/rrr.3450070407

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450070408

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450070409

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450070410

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450070411

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY