Geology topics

Reuben H. Wolff

Publications and source records attributed to Reuben H. Wolff.

9 recordsLinked to original sources

USGS2012

Development of invertebrate community indexes of stream quality for the islands of Maui and Oahu, Hawaii

In 2009-10 the U.S. Geological Survey (USGS) collected physical habitat information and benthic macroinvertebrates at 40 wadeable sites on 25 perennial streams on the Island of Maui, Hawaiʻi, to evaluate the relations between the macroinvertebrate assemblages and environmental characteristics and to develop a multimetric invertebrate community index (ICI) that could be used as an indicator of stream quality. The macroinvertebrate community data were used to identify metrics that could best differentiate among sites according to disturbance gradients such as embeddedness, percent fines (silt and sand areal coverage), or percent agricultural land in the contributing basin area. Environmental assessments were conducted using land-use/land-cover data and reach-level physical habitat data. The Maui data were first evaluated using the previously developed Preliminary-Hawaiian Benthic Index of Biotic Integrity (P-HBIBI) to determine if existing metrics would successfully differentiate stream quality among the sites. Secondly, a number of candidate invertebrate metrics were screened and tested and the individual metrics that proved the best at discerning among the sites along one or more disturbance gradients were combined into a multimetric invertebrate community index (ICI) of stream quality. These metrics were: total invertebrate abundance, Class Insecta relative abundance, the ratio of Trichoptera abundance to nonnative Diptera abundance, native snail (hihiwai) presence or absence, native mountain shrimp (′δpae) presence or absence, native torrent midge ( Telmatogeton spp.) presence or absence, and native Megalagrion damselfly presence or absence. The Maui ICI classified 15 of the 40 sites (37.5 percent) as having "good" quality communities, 17 of the sites (42.5 percent) as having "fair" quality communities, and 8 sites (20 percent) as having "poor" quality communities, a classification that may be used to initiate further investigation into the causes of the poor rating. Additionally, quantitative macroinvertebrate samples collected from 31 randomly selected sites on Oʻahu in 2006-07 as part of the U.S. Environmental Protection Agency's Wadeable Stream Assessment (WSA) were used to refine and develop an ICI of stream quality for Oʻahu. The set of metrics that were included in the revised index were: total invertebrate abundance, Class Insecta relative abundance, the ratio of Trichoptera abundance to nonnative Diptera abundance, turbellarian relative abundance, amphipod relative abundance, nonnative mollusk abundance, and nonnative crayfish ( Procambarus clarkii ) and/or red cherry shrimp ( Neocaridina denticulata sinensis ) presence or absence. The Oʻahu ICI classified 10 of the 31 sites (32.3 percent) as "good" quality communities, 16 of the sites (51.6 percent) as "fair" quality communities, and 5 of the sites (16.1 percent) as "poor" quality communities. A reanalysis of 18 of the Oʻahu macroinvertebrate sites used to develop the P-HBIBI resulted in the reclassification of 3 samples. The beginning of a statewide ICI was developed on the basis of a combination of metrics from the Maui and Oʻahu ICIs. This combined ICI is intended to help identify broad problem areas so that the Hawaii State Department of Health (HIDOH) can prioritize their efforts on a statewide scale. Once these problem areas are identified, the island-wide ICIs can be used to more accurately assess the quality of individual stream reaches so that the HIDOH can prioritize their efforts on the most impaired streams. By using the combined ICI, 70 percent of the Maui sites and 10 percent of the Oʻahu WSA sites were designated as "good" quality sites; 25 percent of the Maui sites and 45 percent of the Oʻahu WSA sites were designated as "fair" quality sites; and 5 percent of the Maui sites and 45 percent of the Oʻahu WSA sites were designated as "poor" quality sites.

Hawai'i↗

USGS2012

Availability and distribution of low flow in Anahola Stream, Kauaʻi, Hawaiʻi

Anahola Stream is a perennial stream in northeast Kauaʻi, Hawaiʻi, that supports agricultural, domestic, and cultural uses within its drainage basin. Beginning in the late 19th century, Anahola streamflow was diverted by Makee Sugar Company at altitudes of 840 feet (upper intake) and 280 feet (lower intake) for irrigating sugarcane in the Keālia area. When sugarcane cultivation in the Keālia area ceased in 1988, part of the Makee Sugar Company’s surface-water collection system (Makee diversion system) in the Anahola drainage basin was abandoned. In an effort to better manage available surface-water resources, the State of Hawaiʻi Department of Hawaiian Home Lands is considering using the existing ditches in the Anahola Stream drainage basin to provide irrigation water for Native Hawaiian farmers in the area. To provide information needed for successful management of the surface-water resources, the U.S. Geological Survey investigated the availability and distribution of natural low flow in Anahola Stream and also collected low-flow data in Goldfish Stream, a stream that discharges into Kaneha Reservoir, which served as a major collection point for the Makee diversion system. Biological surveys of Anahola Stream were conducted as part of a study to determine the distribution of native and nonnative aquatic stream fauna. Results of the biological surveys indicated the presence of the following native aquatic species in Anahola Stream: ʻoʻopu ʻakupa (Sandwich Island sleeper) and ʻoʻopu naniha (Tear-drop goby) in the lower stream reaches surveyed; and ʻoʻopu nākea (Pacific river goby), ʻoʻopu nōpili (Stimpson’s goby), and ʻōpae kalaʻole (Mountain shrimp) in the middle and upper stream reaches surveyed. Nonnative aquatic species were found in all of the surveyed stream reaches along Anahola Stream. The availability and distribution of natural low flow were determined using a combination of discharge measurements made from February 2011 to May 2012 at low-flow partial-record and seepage-run stations established at locations of interest along study-area streams. Upstream of the upper intake, the estimated natural (undiverted) median flow in Anahola Stream is 2.7 million gallons per day, and the flow is expected to be greater than or equal to 0.97 million gallons per day 95 percent of the time. About 0.7 mile upstream of the lower intake and downstream from the confluence with Keaʻoʻopu Stream, the estimated natural (undiverted) median flow in Anahola Stream is 6.3 million gallons per day, and the flow is expected to be greater than or equal to 2.7 million gallons per day 95 percent of the time. In Goldfish Stream, about 0.4 mile upstream from the point of discharge into Kaneha Reservoir, the estimated natural median flow is 0.54 million gallons per day, and the flow is expected to be greater than or equal to 0.23 million gallons per day 95 percent of the time. The discharge estimates are representative of low-flow conditions in the study-area streams, and they are applicable to the base period (water years 1961–2011) over which they have been computed. The distribution of natural low flow in Anahola Stream was characterized through data collected during wet- and dry-season seepage runs. Seepage-run results show that Anahola Stream was generally a gaining stream under natural low-flow conditions. During the wet-season seepage run, Anahola Stream at the station located upstream of tributary Kaʻalula Stream had more than five times the flow that was measured upstream from the upper intake. The estimated total gain (including tributary inflow) in the 6.1-mile seepage-run reach was 6.97 million gallons per day; about 42 percent of that gain was groundwater discharge to the main channel of Anahola Stream. During the dry-season seepage run, about 34 percent of the estimated total gain of 3.93 million gallons per day in the same seepage-run reach was groundwater discharge to the main channel of Anahola Stream. A 15-percent seepage loss was estimated in a 0.3-mile reach downstream from the confluence of Anahola and Keaʻoʻopu Streams. The report summarizes scenarios that describe (1) surface-water availability under regulated conditions of Anahola Stream if the upper and lower intakes are restored in the future; and (2) amount of flow available for agricultural use at the upper intake under a variety of potential instream-flow standards that may be established by the State of Hawaiʻi for the protection of instream uses.

Hawai'i↗

USGS2010

Effects of surface-water diversion on streamflow, recharge, physical habitat, and temperature, Na Wai Eha, Maui, Hawai'i

The perennial flow provided by Waihe‘e River, Waiehu Stream, ‘Īao Stream, and Waikapū Stream, collectively known as Nā Wai ‘Ehā (“The Four Streams”), made it possible for widespread agricultural activities to flourish in the eastern part of West Maui, Hawai‘i. The streams of the Nā Wai ‘Ehā area flow in their upper reaches even during extended dry-weather conditions because of persistent groundwater discharge to the streams. Overall, the lower reaches of these streams lose water, which may contribute to groundwater recharge. During climate years 1984–2007 (when complete streamflow records were available for Waihe‘e River and ‘Īao Stream), Waihe‘e River had the greatest median flow of the four streams upstream of the uppermost diversion on each stream. The median flows, in million gallons per day, during climate years 1984–2007 were: 34 for Waihe‘e River near an altitude of 605 feet; 25 for ‘Īao Stream near an altitude of 780 feet; and estimated to be 4.3 for Waikapū Stream near an altitude of 1,160 feet; 3.2 for North Waiehu Stream near an altitude of 880 feet; and 3.2 for South Waiehu Stream near an altitude of 870 feet. Existing stream diversions in the Nā Wai ‘Ehā area have a combined capacity exceeding at least 75 million gallons per day and are capable of diverting all or nearly all of the dry-weather flows of these streams, leaving some downstream reaches dry. Hourly photographs collected during 2006–2008 indicate that some stream reaches downstream of diversions are dry more than 50 percent of the time. Many of these reaches would be perennial or nearly perennial in the absence of diversions. A lack of sufficient streamflow downstream of existing diversions has led to recent conflicts between those currently diverting or using the water and those desiring sufficient instream flows for protection of traditional and customary Hawaiian rights (including the cultivation of taro), maintenance of habitat for native stream fauna, recreation, aesthetics, and groundwater recharge from loss of water through the streambed. In response to a need for additional information, the U.S. Geological Survey (USGS) undertook the present investigation to characterize the effects of existing surface-water diversions on (1) streamflow, (2) potential groundwater recharge from the streams to the underlying groundwater body, (3) physical habitat for native stream fauna (fish, shrimp, and snails), and (4) instream temperatures. Information collected for this study includes discharge measurements under different streamflow conditions to characterize streamflow and seepage losses, hourly photographs of stream conditions from mounted cameras, snorkel surveys of stream fauna, measurements of microhabitat (depth, velocity, and substrate) under different flow conditions, and measurements of water temperatures. Families of curves were developed to show the relations between surface-water diversion intake capacity (the maximum rate that an intake can divert) and (1) selected duration discharges for sites near the coast; (2) selected duration discharges for the diversions; (3) groundwater-recharge reduction; and (4) physical-habitat reduction for native stream fauna. These curves may be used by water managers to evaluate the effects of different diversion intake capacities on streamflow, water available for offstream use, groundwater recharge, and habitat for native stream fauna.

Hawaii↗

USGS2009

Ecological assessment of wadeable streams on O`ahu, Hawai'i, 2006-2007: A pilot study

In 2006–07, the U.S. Geological Survey (USGS) Pacific Islands Water Science Center (PIWSC), in cooperation with the Hawai‘i Department of Health (HDOH), conducted a pilot study as a participant in the U.S. Environmental Protection Agency’s (USEPA) Wadeable Streams Assessment (WSA) program. Forty randomly selected sites on perennial streams on O‘ahu, Hawai‘i, were surveyed for habitat characteristics, water chemistry, and benthic macroinvertebrate assemblages. Of the original sampling frame of approximately 505.2 miles of perennial stream, roughly 96.7±30.7 miles were found to be nonperennial or estuarine and another 200.5±64.7 miles were judged to be inaccessible. The scope of this report presents an assessment of the remaining 208±57.6 miles of accessible, wadeable, perennial stream length on O‘ahu. Benthic macroinvertebrate assemblages were used to determine the ecological condition at each site. Components of the benthic macroinvertebrate assemblages were assessed using the multimetric Preliminary–Hawaiian Benthic Index of Biotic Integrity (P–HBIBI) developed by Wolff (2005). Based on the P–HBIBI scores, an estimated 5.8±5.8 percent of the island’s total stream length is in most disturbed condition, 56±13.5 percent is in intermediately disturbed condition, and 38.2±13.2 percent is in least disturbed condition. Windward O‘ahu had the highest percentage of stream length in least disturbed biological condition at 56.7±20.8 percent. Using the relative abundance of insects, one of the core metrics that make up the P–HBIBI, 43.4±14.2 percent of the islandwide stream length was classified in the most disturbed condition—52±31.2 percent of the Honolulu region stream length and 51.4±23.3 percent of the windward O‘ahu stream length. An analysis of total nitrogen (N) estimated approximately 41.1±13.7 percent of the stream length on O‘ahu was in most disturbed condition. Regionally, the Honolulu region had the largest proportion, 61.3±28.6 percent, of most disturbed stream length in terms of total N. An analysis of total phosphorus (P) classified approximately 43.2±14 percent of the stream length on O‘ahu as most disturbed. Regionally, windward O‘ahu had the largest proportion, 78.4±19.5 percent, of stream length classified as most disturbed. An analysis of embeddedness classified 30.3±14.7 percent of O‘ahu’s stream length as most. Regionally, windward O‘ahu had the largest proportion, 43.3±17.1 percent, of stream length classified as most disturbed as compared to the reference condition. An analysis of riparian disturbance, an index of the in-channel, riparian, and near-stream human activities, classified 43±13 percent of stream length on O‘ahu as most disturbed. The Honolulu region had the largest proportion of stream length, 86.3±13.7 percent, classified as most disturbed. The information in this report is the first attempt in Hawai‘i to assess the islandwide ecological condition of wadeable, perennial streams on O‘ahu using the USEPA WSA probabilistic design. This study has demonstrated that such an assessment is practical and that it can provide information that may help the USEPA and HDOH in determining the status of aquatic ecosystems on O‘ahu, Hawai‘i. This study provides a baseline assessment of the current islandwide ecological condition and identifies potential environmental stressors. It can be used, with future WSA studies in Hawai‘i, to measure the changes in those conditions and the effectiveness of management efforts to protect, restore, and maintain Hawai‘i’s aquatic environment.

Hawaii↗

USGS2008

Effects of the H-3 Highway stormwater runoff on the water quality of Halawa Stream, Oahu, Hawaii, November 1998 to August 2004

Since November 1998, water-quality data have been collected from the H-3 Highway Storm Drain C, which collects runoff from a 4-mi-long viaduct, and from Halawa Stream on Oahu, Hawaii. From January 2001 to August 2004, data were collected from the storm drain and four stream sites in the Halawa Stream drainage basin as part of the State of Hawaii Department of Transportation Storm Water Monitoring Program. Data from the stormwater monitoring program have been published in annual reports. This report uses these water-quality data to explore how the highway storm-drain runoff affects Halawa Stream and the factors that might be controlling the water quality in the drainage basin. In general, concentrations of nutrients, total dissolved solids, and total suspended solids were lower in highway runoff from Storm Drain C than at stream sites upstream and downstream of Storm Drain C. The opposite trend was observed for most trace metals, which generally occurred in higher concentrations in the highway runoff from Storm Drain C than in the samples collected from Halawa Stream. The absolute contribution from Storm Drain C highway runoff, in terms of total storm loads, was much smaller than at stations upstream and downstream, whereas the constituent yields (the relative contribution per unit drainage basin area) at Storm Drain C were comparable to or higher than storm yields at stations upstream and downstream. Most constituent concentrations and loads in stormwater runoff increased in a downstream direction. The timing of the storm sampling is an important factor controlling constituent concentrations observed in stormwater runoff samples. Automated point samplers were used to collect grab samples during the period of increasing discharge of the storm throughout the stormflow peak and during the period of decreasing discharge of the storm, whereas manually collected grab samples were generally collected during the later stages near the end of the storm. Grab samples were analyzed to determine concentrations and loads at a particular point in time. Flow-weighted time composite samples from the automated point samplers were analyzed to determine mean constituent concentrations or loads during a storm. Chemical analysis of individual grab samples from the automated point sampler at Storm Drain C demonstrated the “first flush” phenomenon—higher constituent concentrations at the beginning of runoff events—for the trace metals cadmium, lead, zinc, and copper, whose concentrations were initially high during the period of increasing discharge and gradually decreased over the duration of the storm. Water-quality data from Storm Drain C and four stream sites were compared to the State of Hawaii Department of Health (HDOH) water-quality standards to determine the effects of highway storm runoff on the water quality of Halawa Stream. The geometric-mean standards and the 10- and 2-percent-of-the-time concentration standards for total nitrogen, nitrite plus nitrate, total phosphorus, total suspended solids, and turbidity were exceeded in many of the comparisons. However, these standards were not designed for stormwater sampling, in which constituent concentrations would be expected to increase for short periods of time. With the aim of enhancing the usefulness of the water-quality data, several modifications to the stormwater monitoring program are suggested. These suggestions include (1) the periodic analyzing of discrete samples from the automated point samplers over the course of a storm to get a clearer profile of the storm, from first flush to the end of the receding discharge; (2) adding an analysis of the dissolved fractions of metals to the sampling plan; (3) installation of an automatic sampler at Bridge 8 to enable sampling earlier in the storms; (4) a one-time sampling and analysis of soils upstream of Bridge 8 for base-line contaminant concentrations; (5) collection of samples from Halawa Stream during low-flow conditions to determine base-line conditions; (6) addition of the dissolved fraction of the metals chromium and nickel to the sampling plan; (7) elimination of fecal coliform and biochemical oxygen demand (BOD) analyses from the sampling plan; and (8) a study to examine the efficiency of the highway street sweeping.

Hawaii↗

USGS2006

Effects of Surface-Water Diversion and Ground-Water Withdrawal on Streamflow and Habitat, Punaluu Stream, Oahu, Hawaii

The surface- and ground-water resources of the Punaluu area of northeast Oahu, Hawaii, have been and continue to be important for cultural, domestic, agricultural, recreational, and aesthetic purposes. Punaluu Stream flows perennially because rain falls frequently in the area and ground water discharges to the stream. Flow in Punaluu Stream is reduced by the direct diversion of water for off-stream uses and possibly from the withdrawal of ground water near the stream. Punaluu Ditch diverts water from Punaluu Stream near an altitude of 210 feet. During the recent period 1995-2004, discharge in Punaluu Stream that was equaled or exceeded 50 percent of the time (median or Q50 discharge) and discharge that was equaled or exceeded 95 percent of the time (Q95 discharge) measured immediately upstream from the Punaluu Ditch diversion intake, respectively, were 18 and 13 cubic feet per second, whereas the Q50 and Q95 discharges measured immediately downstream from the diversion intake, respectively, were 7.0 and 1.3 cubic feet per second. Thus, near an altitude of 210 feet, diversion of surface water by the Punaluu Ditch caused the Q50 discharge in Punaluu Stream to be reduced to 39 percent of the natural Q50 discharge, and the Q95 discharge was reduced to 10 percent of the natural value. The relative effects of the Punaluu Ditch diversion on flow in Punaluu Stream decreased in a downstream direction, mainly because of the compensating effects of tributary inflows and ditch return flows. At an altitude of 10 feet, the Q50 discharge in Punaluu Stream was 82 percent of the natural Q50 discharge, and the Q95 discharge was 69 percent of the natural value. Changes in streamflow affect the quantity and quality of physical habitat used by native stream fauna. The Physical Habitat Simulation System (PHABSIM) approach was used to evaluate the effects of different diversion scenarios on physical habitat for selected native species in Punaluu Stream. Habitat-suitability criteria developed for streams in northeast Maui, Hawaii, were used to determine the effects of incremental changes in streamflow on physical habitat, in terms of weighted usable area (WUA) in Punaluu Stream. The effects of different diversion conditions on WUA for Neritina granosa and Awaous guamensis were evaluated by determining the average number of days per year for which WUA values are less than a specified reference value (during periods when discharge is less than or equal to the median natural discharge). For recent diverted conditions (1995-2004), the average number of days per year that WUA values are less than 50 or 75 percent of the WUA value at median natural discharge generally (1) decreases in a downstream direction, reflecting the effects of tributary inflows and ditch return flows, (2) is less than the corresponding number of days for constant diversion rates greater than about 4-5 cubic feet per second at a stream altitude of 10 feet, and (3) is greater than the corresponding number of days for a constant diversion rate of 10 cubic feet per second at stream altitudes of 40, 100, and 140 feet. The number of days that WUA values are less than 75 percent of the WUA value at median natural discharge generally increases substantially for constant diversion rates exceeding about 4-5 cubic feet per second. At stream altitudes of 10, 40, 100, and 200 feet and for constant diversion rates of up to 4 cubic feet per second, WUA values are less than 75 percent of the WUA value at median natural discharge for fewer than 13 days per year. At stream altitudes above 40 feet and for a constant diversion rate of 10 cubic feet per second, WUA values are less than 75 percent of the WUA value at median natural discharge for 131 to 183 days per year. Stream temperature is a factor that potentially could affect the abundance and distribution of native aquatic species. Measured stream temperatures immediately upstream and downstream from the diversion intake did not indicat

Scientific Investigations Report↗

USGS2005

Feasibility of using benthic invertebrates as indicators of stream quality in Hawaii

Macroinvertebrates were collected from 19 sites on 14 streams on the island of Oahu and from 9 sites on 7 streams on the island of Kauai to evaluate associations between macroinvertebrate assemblages and environmental variables and to determine whether or not it would be feasible, in future studies, to develop macroinvertebrate metrics that would indicate stream quality based on the macroinvertebrate assemblages and/or components of the assemblages. The purpose of applying rapid bioassessment techniques is to identify stream quality problems and to document changes in stream quality. Samples were collected at 10 sites in 1999, 3 sites in 2000, and 5 sites in 2003 on Oahu and at 9 sites on Kauai in 2003. Additionally, multiple year and multiple reach samples were collected at 1 site on Oahu. Macroinvertebrates were collected primarily from boulder/cobble riffles or from the fastest flowing habitat when riffles were absent. Although most streams in Hawaii originate in mountainous, forested areas, the lower reaches often drain urban, agricultural, or mixed land-use areas. The macroinvertebrate community data were used to identify metrics that could best differentiate between sites according to levels of environmental impairment. Environmental assessments were conducted using land-use/land-cover data, bed-sediment and fish-tissue contaminant data, and reach-level environmental data using a calibration set of 15 sites. The final scores of the environmental assessments were used to classify the sites into three categories of impairment: mild, moderate or severe. A number of invertebrate metrics were then tested and calibrated to the environmental assessments scores. The individual metrics that were the best at discerning environmental assessments among the sites were combined into a multimetric benthic index of biotic integrity (BIBI). These metrics were: total invertebrate abundance, taxa richness, insect relative abundance, amphipod abundance, crayfish presence or absence, and native mountain shrimp presence or absence. Because this index is in the preliminary stage of development and additional 'pristine' sites need to be sampled and assessed to develop a more robust measure of biotic integrity, the index will be referred to as a Preliminary Hawaiian Benthic Index of Biotic Integrity (P-HBIBI). The P-HBIBI scores were then classified into three categories of impairment: mild, moderate, or severe. The P-HBIBI was then used to assess the remaining sites and classify them into impairment categories. The P-HBIBI was correlated (r2 = 0.72; p < 0.005) with a reduced environmental assessment determined without contaminants data. The results of this study suggest that the development of a reliable Hawaiian benthic index of biotic integrity (HBIBI), based on macroinvertebrate assemblages, is feasible; however, a much larger sample size, including more samples from 'pristine' sites and from the other islands, would be required.

Scientific Investigations Report↗

USGS2005

Effects of Surface-Water Diversions on Habitat Availability for Native Macrofauna, Northeast Maui, Hawaii

Effects of surface-water diversions on habitat availability for native stream fauna (fish, shrimp, and snails) are described for 21 streams in northeast Maui, Hawaii. Five streams (Waikamoi, Honomanu, Wailuanui, Kopiliula, and Hanawi Streams) were chosen as representative streams for intensive study. On each of the five streams, three representative reaches were selected: (1) immediately upstream of major surface-water diversions, (2) midway to the coast, and (3) near the coast. This study focused on five amphidromous native aquatic species (alamoo, nopili, nakea, opae, and hihiwai) that are abundant in the study area. The Physical Habitat Simulation (PHABSIM) System, which incorporates hydrology, stream morphology and microhabitat preferences to explore relations between streamflow and habitat availability, was used to simulate habitat/discharge relations for various species and life stages, and to provide quantitative habitat comparisons at different streamflows of interest. Hydrologic data, collected over a range of low-flow discharges, were used to calibrate hydraulic models of selected transects across the streams. The models were then used to predict water depth and velocity (expressed as a Froude number) over a range of discharges up to estimates of natural median streamflow. The biological importance of the stream hydraulic attributes was then assessed with the statistically derived suitability criteria for each native species and life stage that were developed as part of this study to produce a relation between discharge and habitat availability. The final output was expressed as a weighted habitat area of streambed for a representative stream reach. PHABSIM model results are presented to show the area of estimated usable bed habitat over a range of streamflows relative to natural conditions. In general, the models show a continuous decrease in habitat for all modeled species as streamflow is decreased from natural conditions. The PHABSIM modeling results from the intensively studied streams were normalized to develop relations between the relative amount of diversion from a stream and the resulting relative change in habitat in the stream. These relations can be used to estimate changes in habitat for diverted streams in the study area that were not intensively studied. The relations indicate that the addition of even a small amount of water to a dry stream has a significant effect on the amount of habitat available. Equations relating stream base-flow changes to habitat changes can be used to provide an estimate of the relative habitat change in the study area streams for which estimates of diverted and natural median base flow have been determined but for which detailed habitat models were not developed. Stream water temperatures, which could have an effect on stream ecology and taro cultivation, were measured in five streams in the study area. In general, the stream temperatures measured at any of the monitoring sites were not elevated enough, based on currently available information, to adversely effect the growth or mortality of native aquatic macrofauna or to cause wetland taro to be susceptible to fungi and associated rotting diseases.

Scientific Investigations Report↗

USGS2003

Associations among land-use, habitat characteristics, and invertebrate community structure in nine streams on the island of Oahu, Hawaii

The island of Oahu is one of 51 study units established as part of the U.S. Geological Surveys National Water-Quality Assessment (NAWQA) program to assess the status and trends of the Nations surface and ground-water resources, and to link status and trends with an understanding of the natural and human factors that affect water quality. As part of the NAWQA program, benthic invertebrate communities were surveyed at ten sites in nine streams representing the three main types of land use on Oahu: urban, agriculture, and forested. At each sampling site, habitat characteristics were determined at a range of spatial scales including drainage basin, segment, reach, transect, and point. Associations among land use, habitat characteristics, and benthic invertebrate community structure were examined. The rapid population growth and increasing urbanization on Oahu has resulted in substantial stream habitat alteration. Instream habitat characteristics at the urban and mixed (urban and agriculture) land-use sites were markedly different from those at the forested sites. Urban and mixed land-use sites, most of which were channelized, tended to have less riparian vegetation, higher water temperatures, smaller substrate, and higher levels of embeddedness and siltation than sites in forested watersheds. The majority of invertebrate taxa identified during this study were non-native. Invertebrate abundance was lower at urban and mixed land-use sites than at forested sites, while species richness (the number of different species) showed the opposite pattern. Multivariate analyses indicated that invertebrate species composition was similar at sites with similar land use. Aquatic insects of the orders Diptera and Trichoptera were the most common insects in all samples. The ratio of Diptera to Trichoptera abundance varied with urbanization. Forested sites were dominated by Trichoptera, and urban and mixed land-use sites were dominated by Diptera. Molluscs typically occurred in channelized urban streams although no native molluscs were collected during this study. The most abundant molluscs were pan-tropical thiarid snails, the introduced clam Corbicula fluminea, and the limpet Ferrissia sharpi. Two native and four introduced species of Crustacea were collected at the sampling sites. To effectively manage Hawaiian watersheds for native species and the communities they form, the ways in which these species respond to human-induced changes needs to be understood. This report provides important information describing the usefulness of invertebrates as indicators of stream quality conditions and how an integrated assessment of stream quality will allow for the development of appropriate monitoring and management strategies.

Water-Resources Investigations Report↗