Eutrophication in the River Meuse

The severe problems caused by large phytoplankton populations in the River Meuse date back to the beginning of the 1980s. However, no clear relationship can be established between an increase of algal growth and dissolved nutrient concentrations, at least in the Belgian part of the river. Most probably, plankton algae start developing in France, utilizing large inputs of phosphorus from some of the tributaries: this point will be investigated further, as well as the effect of a reduction in the releases of phosphorus. A mathematical model helps to understand the main factors which control algal growth: underwater light, temperature, discharge and grazing by zooplankton. The last is a major loss process in summer and, as shown by recent observations, may trigger a seasonal succession leading to dominance by large phytoplankton taxa. With regard to water quality, eutrophication is a major problem in drinking-water treatment (filter clogging, etc.) and large numbers of decomposing algae may adversely affect the oxygen budget of the river. On the other hand, algal photosynthesis is the most important oxygen source at periods of low discharge, and reduced algal production may result in dramatic oxygen decreases in heavily polluted stretches of the river.

Marine biology of the Sierra Leone River Estuary. 1. The physical environment

The Sierra Leone River Estuary is a relatively young drowned river valley, it is shallow except for a deep channel which passes close to the Freetown shoreline. The upper reaches merge into a network of creeks and channels fringed by large areas of mangrove swamps. It is a tidal estuary of the semi-mixed type with the saline oceanic water entering it on a diurnal cycle. The climate of Sierra Leone is marked by a very distinct change between a very wet rainy season and a dry season. The tidal range of the Estuary (spring 3.03m; neap 2.28m) does not impede normal use of the harbour. The tidal variations can be felt as far as 42 miles inland along the water courses of the Sierra Leone River and its tributaries. The volume of fresh water entering the Estuary is large during the rainy season and greatly reduced during the dry season. Consequently there is a marked fall in salinity during the rainy season and higher salinities due to the marine influence prevailing during the dry season. The nature of the shores and bottom, the hydrography and chemistry of the estuarine system have been outlined in relation to the prevailing climatic conditions.

Juvenile salmon investigations River Wenning catchment 1981-86

As part of the River Lune juvenile salmonid investigation, a number of sites on the River Wenning catchment were electrofished annually from 1981 - 1985. Particularly low Salmon parr populations were evident for much of the Wenning catchment which has caused some concern. All the Wenning catchment electrofishing results are reported in this paper and comparisons are made with designated groups of sites on the remainder of the Lune catchment. These groups of sites are: River Lune and tributaries, upstream Tebay, Upper Middle Lune, Lower Middle Lune, Lower Lune, Birk & Borrow Becks, Chapel & Crosdale Becks, Rawthey system, Barbon & Leek Becks and the Greta system. The general scarcity of Salmonids in large sections of the main river Wenning probably reflects the apparent limited natural spawning areas on the catchment. Details of Salmon fry and ova planting on the Wenning catchment since 1981 have been collated and whilst survival through the 0+ stage appears to be quite good, recruitment to the 1++ stage appears to be poor. Water quality does not appear to be responsible for the very low salmonid densities at some main river sites but is possibly a factor in apparently preventing any Salmon run in Keasden Beck. Recommendations for future Fisheries and Biological work are given.

An investigation of the recaptures rates for tagged brown trout stocked into the River Ribble

The angling season for non-migratory brown trout, in the Environment Agency (EA) North West Region, runs from March 15th to September 30th. Each year, large numbers of farm reared brown trout are stocked into the rivers of the North West Region's Central Area. In 1994, approximately 20,000 brown trout were introduced into the River systems of the Lune, Wyre and Ribble by local angling clubs and fishery owners. Most of these fish were stocked at a length greater than that defined by local byelaws as the takeable size (200mm). Introductions are made to supplement the existing wild brown trout populations within the river and increase the probability of an angler catching a fish. Stocking with fish of a sufficient length allows the successful angler to remove the catch for their own use. In this way, stretches of the rivers are effectively managed as "put and take" fisheries for brown trout. A number of brown trout fingerlings are also introduced each year by angling clubs and fishery owners. These are stocked with the expectation that the fish will survive in the river to grow, over-winter, and eventually attain a takable size with an increased degree of "wildness". The lower cost of fingerlings, as opposed to trout of a takable length, makes their introduction more attractive to angling clubs since a greater number can be stocked for a given cost. Although the practise of stocking brown trout has occurred for many years in the Central Area, there is little information of its success in terms of increasing anglers catches, or the survival offish introduced. This study was initiated to determine the recapture rates by angling of brown trout following their introduction into a river fishery. The information gained from this study can then be used to give guidance to angling clubs and fishery owners on the optimal strategies for stocking fish.

Geomorphological considerations for the introduction of boulders and groynes for fisheries enhancement: assessment of River Eden at Carhead

This report seeks to briefly provide geomorphological guidance over the introduction of 'habitat enhancement' features for fisheries improvement which is an expanding area of interest throughout the region. This document is a primary attempt to draw together the salient details from the large quantity of literature published in recent years with reference to boulder introduction and to groyne/deflector placement in NW rivers. Secondly the potential introduction of such features is assessed, with reference to the proposed works at Carhead on the Eden.

An analysis of salmon rod catch data from castle fisheries, River Derwent, 1923-1989.

The aim of this study was to investigate the historical catch record from the Castle Fishery on the River Derwent over the period 1923 - 1989, to determine if changes had taken place in the composition of the catch and to examine the influence of flow on the performance of the fishery. The River Derwent is situated in West Cumbria, North West England. It flows from its source on Scafell Pike (NGR NY 229 089) westwards discharging into the Irish sea at Workington, a distance of 52 km. Over its length it receives water from an additional 214 km of stream, 5 large lakes and approximately 30 small tarns. The catchment drains a total area of 663 km2. The study concludes that through the time period there was considerable variation in catch between years. The trend was for the catch to increase steadily over the period 1923 - 1958, declining rapidly in 1959, after which catches increased steadily reaching a peak in the mid-sixties, before declining towards the end of the decade. During the seventies and eighties catches remained relatively stable at between 300 - 600 salmon per year until 1988 when over 2000 salmon were reported caught, the greatest number in any year over the study period.

Biological report - fish mortality, River Conder, 21.7.79

Following a large scale fish mortality caused by a considerable spillage of a pentachlbrophenol-based disinfectant from a mushroom farm, a biological survey of the river Conder was undertaken on 23.7.79. A spillage of this same make of disinfectant from this mushroom farm in February 1976 caused a similar large scale fish mortality. On that occasion, the pollution appeared to have little effect on the benthic invertebrates of the river Conder, with no dead organisms found, although the small beck which received the spillage was quite badly affected. This recent spillage of disinfectant involved a considerably greater volume (approximately 900 gallons) than the 1976 discharge and so this report looks at whether invertebrate fauna of the main river were affected on this occasion. Kick samples were taken at a number of sites in the river Conder from the confluence with the polluted beck to Conder Green. A control sample was also taken upstream of the confluence with the polluted beck. All samples were examined on site and live and dead invertebrates noted and identified as accurately as possible.

River Dart fisheries survey 1974

This is the River Dart Fisheries Survey 1974 report produced by the South West Water Authority. The survey was carried out between July and October 1974 to assess the extent of the 0+ and 1+ Salmo salar L. population in the Dart catchment and thereby assess directly the success of the 1973/74 and 1972/73 spawning season. The survey showed that there were large numbers of salmon parr distributed throughout the upper reaches of the Dart, reflecting the successful spawning of the 1973/74 and 1972/73 season. It contains tables with survey sections locations, presence/absence for each section and location maps with spawning grounds and sampling stations.

Implications of using On-Farm Flood Flow Capture to recharge groundwater and mitigate flood risks along the Kings River, CA

Two large hydrologic issues face the Kings Basin, severe and chronic overdraft of about 0.16M ac-ft annually, and flood risks along the Kings River and the downstream San Joaquin River. Since 1983, these floods have caused over $1B in damage in today’s dollars. Capturing flood flows of sufficient volume could help address these two pressing issues which are relevant to many regions of the Central Valley and will only be exacerbated with climate change. However, the Kings River has high variability associated with flow magnitudes which suggests that standard engineering approaches and acquisition of sufficient acreage through purchase and easements to capture and recharge flood waters would not be cost effective. An alternative approach investigated in this study, termed On-Farm Flood Flow Capture, involved leveraging large areas of private farmland to capture flood flows for both direct and in lieu recharge. This study investigated the technical and logistical feasibility of best management practices (BMPs) associated with On-Farm Flood Flow Capture. The investigation was conducted near Helm, CA, about 20 miles west of Fresno, CA. The experimental design identified a coordinated plan to determine infiltration rates for different soil series and different crops; develop a water budget for water applied throughout the program and estimate direct and in lieu recharge; provide a preliminary assessment of potential water quality impacts; assess logistical issues associated with implementation; and provide an economic summary of the program. At check locations, we measured average infiltration rates of 4.2 in/d for all fields and noted that infiltration rates decreased asymptotically over time to about 2 – 2.5 in/d. Rates did not differ significantly between the different crops and soils tested, but were found to be about an order of magnitude higher in one field. At a 2.5 in/d infiltration rate, 100 acres are required to infiltrate 10 CFS of captured flood flows. Water quality of applied flood flows from the Kings River had concentrations of COC (constituents of concern; i.e. nitrate, electrical conductivity or EC, phosphate, ammonium, total dissolved solids or TDS) one order of magnitude or more lower than for pumped groundwater at Terranova Ranch and similarly for a broader survey of regional groundwater. Applied flood flows flushed the root zone and upper vadose zone of nitrate and salts, leading to much lower EC and nitrate concentrations to a depth of 8 feet when compared to fields in which more limited flood flows were applied or for which drip irrigation with groundwater was the sole water source. In demonstrating this technology on the farm, approximately 3,100 ac-ft was diverted, primarily from April through mid-July, with about 70% towards in lieu and 30% towards direct recharge. Substantial flood flow volumes were applied to alfalfa, wine grapes and pistachio fields. A subset of those fields, primarily wine grapes and pistachios, were used primarily to demonstrate direct recharge. For those fields about 50 – 75% of water applied was calculated going to direct recharge. Data from the check studies suggests more flood flows could have been applied and infiltrated, effectively driving up the amount of water towards direct recharge. Costs to capture flood flows for in lieu and direct recharge for this project were low compared to recharge costs for other nearby systems and in comparison to irrigating with groundwater. Moreover, the potentially high flood capture capacity of this project suggests significant flood avoidance costs savings to downstream communities along the Kings and San Joaquin Rivers. Our analyses for Terranova Ranch suggest that allocating 25% or more flood flow water towards in lieu recharge and the rest toward direct recharge will result in an economically sustainable recharge approach paid through savings from reduced groundwater pumping. Two important issues need further consideration. First, these practices are likely to leach legacy salts and nitrates from the unsaturated zone into groundwater. We develop a conceptual model of EC movement through the unsaturated zone and estimated through mass balance calculations that approximately 10 kilograms per square meter of salts will be flushed into the groundwater through displacing 12 cubic meters per square meter of unsaturated zone pore water. This flux would increase groundwater salinity but an equivalent amount of water added subsequently is predicted as needed to return to current groundwater salinity levels. All subsequent flood flow capture and recharge is expected to further decrease groundwater salinity levels. Second, the project identified important farm-scale logistical issues including irrigator training; developing cropping plans to integrate farming and recharge activities; upgrading conveyance; and quantifying results. Regional logistical issues also exist related to conveyance, integration with agricultural management, economics, required acreage and Operation and Maintenance (O&M).

Seasonal and interannual variation in juvenile salmonids and associated fish assemblage in open waters of the lower Columbia River estuary

The transition between freshwater and marine environments is associated with high mortality for juvenile anadromous salmonids, yet little is known about this critical period in many large rivers. To address this deficiency, we investigated the estuarine ecology of juvenile salmonids and their associated fish assemblage in open-water habitats of the lower Columbia River estuary during spring of 2007–10. For coho (Oncorhynchus kisutch), sockeye (O. nerka), chum (O. keta), and yearling (age 1.0) Chinook (O. tshawytscha) salmon, and steelhead (O. mykiss), we observed a consistent seasonal pattern characterized by extremely low abundances in mid-April, maximum abundances in May, and near absence by late June. Subyearling (age 0.0) Chinook salmon were most abundant in late June. Although we observed interannual variation in the presence, abundance, and size of juvenile salmonids, no single year was exceptional across all species-and-age classes. We estimated that >90% of juvenile Chinook and coho salmon and steelhead were of hatchery origin, a rate higher than previously reported. In contrast to juvenile salmonids, the abundance and composition of the greater estuarine fish assemblage, of which juvenile salmon were minor members, were extremely variable and likely responding to dynamic physical conditions in the estuary. Comparisons with studies conducted 3 decades earlier suggest striking changes in the estuarine fish assemblage—changes that have unknown but potentially important consequences for juvenile salmon in the Columbia River estuary.

An ecological characterization of Salt River Bay National Historical Park and Ecological Preserve, U.S. Virgin Islands

Salt River Bay National Historical Park and Ecological Preserve (hereafter, SARI or the park) was created in 1992 to preserve, protect, and interpret nationally significant natural, historical, and cultural resources (United States Congress 1992). The diverse ecosystem within it includes a large mangrove forest, a submarine canyon, coral reefs, seagrass beds, coastal forests, and many other natural and developed landscape elements. These ecosystem components are, in turn, utilized by a great diversity of flora and fauna. A comprehensive spatial inventory of these ecosystems is required for successful management. To meet this need, the National Oceanic and Atmospheric Administration (NOAA) Biogeography Program, in consultation with the National Park Service (NPS) and the Government of the Virgin Islands Department of Planning and Natural Resources (VIDPNR), conducted an ecological characterization. The characterization consists of three complementary components: a text report, digital habitat maps, and a collection of historical aerial photographs. This ecological characterization provides managers with a suite of tools that, when coupled with the excellent pre-existing body of work on SARI resources, enables improved research and monitoring activities within the park (see Appendix F for a list of data products).

Southern California's megaflood event of ca. 1605 AD linked to large-scale atmospheric forcing

A distinct, 1- to 2-cm-thick flood deposit found in Santa Barbara Basin with a varve-date of 1605 AD ± 5 years testifies to an intensity of precipitation that remains unmatched for later periods when historical or instrumental records can be compared against the varve record. The 1605 AD ± 5 event correlates well with Enzel's (1992) finding of a Silver Lake playa perennial lake at the terminus of the Mojave River (carbon-14-dated 1560 AD ± 90 years), in relative proximity to the rainfall catchment area draining into Santa Barbara Basin. According to Enzel, such a persistent flooding of the Silver Lake playa occurred only once during the last 3,500 years and required a sequence of floods, each comparable in magnitude to the largest floods in the modern record. To gain confidence in dating of the 1605 AD ± 5 event, we compare Southern California's sedimentary evidence against historical reports and multi-proxy time-series that indicate unusual climatic events or are sensitive to changes in large-scale atmospheric circulation patterns. The emerging pattern supports previous suggestions that the first decade of the 17th century was marked by a rapid cooling of the Northern Hemisphere, with some indications for global coverage. A burst of volcanism and the occurrence of El Nino seem to have contributed to the severity of the events. The synopsis of the 1605 AD ± 5 years flood deposit in Santa Barbara Basin, the substantial freshwater body at Silver Lake playa, and much additional paleoclimatic, global evidence testifies for an equatorward shift of global wind patterns as the world experienced an interval of rapid, intense, and widespread cooling.

Larval development of the southern sea garfish (Hyporhamphus melanochir) and the river garfish (H. regularis) (Beloniformes: Hemiramphidae) from South Australian waters

Larval development of the southern sea garfish (Hyporhamphus melanochir) and the river garfish (H. regularis) is described from specimens from South Australian waters. Larvae of H. melanochir and H. regularis have completed notochord flexion at hatching and are characterized by an elongate body with distinct rows of melanophores along the dorsal, lateral, and ventral surfaces; a small to moderate head; a heavily pigmented and long straight gut; a persistent pre-anal finfold; and an extended lower jaw. Fin formation occurs in the following sequence: caudal, dorsal and anal (almost simultaneously), pectoral, and pelvic. Despite the similarities between both species and among hemiramphid larvae in general, H. melanochir larvae are distinguishable from H. regularis by 1) having 58–61 vertebrae (vs. 51–54 for H. regularis); 2) having 12–15 melanophore pairs in longitudinal rows along the dorsal margin between the head and origin of the dorsal fin (vs. 19–22 for H. regularis); and 3) the absence of a large ventral pigment blotch anteriorly on the gut and isthmus (present in H. regularis). Both species can be distinguished from similar larvae of southern Australia (other hemiramphids and a scomberosocid) by differences in meristic counts and pigmentation.

Genetic analysis of juvenile coho salmon (Oncorhynchus kisutch) off Oregon and Washington reveals few Columbia River wild fish

Little is known about the ocean distributions of wild juvenile coho salmon off the Oregon-Washington coast. In this study we report tag recoveries and genetic mixed-stock estimates of juvenile fish caught in coastal waters near the Columbia River plume. To support the genetic estimates, we report an allozyme-frequency baseline for 89 wild and hatchery-reared coho salmon spawning populations, extending from northern California to southern British Columbia. The products of 59 allozyme-encoding loci were examined with starch-gel electrophoresis. Of these, 56 loci were polymorphic, and 29 loci had P0.95 levels of polymorphism. Average heterozygosities within populations ranged from 0.021 to 0.046 and averaged 0.033. Multidimensional scaling of chord genetic distances between samples resolved nine regional groups that were sufficiently distinct for genetic mixed-stock analysis. About 2.9% of the total gene diversity was due to differences among populations within these regions, and 2.6% was due to differences among the nine regions. This allele-frequency data base was used to estimate the stock proportions of 730 juvenile coho salmon in offshore samples collected from central Oregon to northern Washington in June and September-October 1998−2000. Genetic mixed-stock analysis, together with recoveries of tagged or fin-clipped fish, indicates that about one half of the juveniles came from Columbia River hatcheries. Only 22% of the ocean-caught juveniles were wild fish, originating largely from coastal Oregon and Washington rivers (about 20%). Unlike previous studies of tagged juveniles, both tag recoveries and genetic estimates indicate the presence of fish from British Columbia and Puget Sound in southern waters. The most salient feature of genetic mixed stock estimates was the paucity of wild juveniles from natural populations in the Columbia River Basin. This result reflects the large decrease in the abundances of these populations in the last few decades.

Satellite passive microwave observations of the upper Colorado River snowpack

Seasonal snow cover in the mountains of the Upper Colorado River Basin is a major source of water for a large portion of the southwestern United States. The extent and amount of this snowpack not only reflects changes in weather patterns and climate but also influences the general circulation through modification of the energy exchange between land and atmosphere. ... Satellite observations and remote sensing techniques can enhance the standard snowpack observations to provide the temporal and spatial measurements required for understanding the role of snow in the surface energy balance and improving the management of water resources.