jurate landwehr - Academia.edu (original) (raw)

Papers by jurate landwehr

Estuaries, Jun 1, 1994

ABSTRACT: Weather and water-quality data from 1980 to 1989 were correlated with fluctuations in s... more ABSTRACT: Weather and water-quality data from 1980 to 1989 were correlated with fluctuations in submersed mac-rophyte populations in the tidal Potomac River near Washington, DC, to elucidate causal relationships and explain population dynamics. Both reaches were unvegetated in ...

Water Resources Research, Apr 1, 1979

Water quality indices are treated as random variables; the •class of quality 'averaging' indices ... more Water quality indices are treated as random variables; the •class of quality 'averaging' indices is examined and several statistics are derived. It is seen that the prob•'bility density functions of the water quality constituents as well as the structure of the transform functions (rating curves) influence the ability of indices to measure policy performance. This paper is not subject to U.S. copyright. Published in 1979 by the American Geophysical Union. geometric average, or the extreme value, upon the several constituent levels, all expressed in terms of quality units. The second category of indices encompasses definitions which also include a transformation step, but the transform functions are explicitly constructed to reflect the number or magnitude of violations of some set of standards. Such indices have been proposed by Nemerow and Sumitomo [1970] and Environmental Protection Agency (EPA) Region VIII [Enoironmental Protection Agency, 1973]. In addition, there are hybrids of the first and second kinds, including those proposed by EPA Region X [Beebe, 1975] and Stoner [1978]. A wide variety of mathematical structures can be found among the members of the third index category. These include efforts to formulate indices based on factor analysis [Shoji et al., 1966; Drobny, 1971], principle component analysis [Rogers, 1971], and Kendall's [1955] multivariate ranking procedure [Harkins, 1974; Shaeffer and Janardan, 1977]. Note that a more detailed discussion of the literature can be found in the work of Landwehr [1974].

Sources of fine-grained suspended sediment in the Pocomoke River watershed draining above Willard... more Sources of fine-grained suspended sediment in the Pocomoke River watershed draining above Willards, Maryland, were identified using a 'sediment-fingerprinting' approach. Potential sediment sources in the watershed were cropland, forest, channel and ditch banks, and ditch beds. Samples of fine-grained suspended sediment were obtained for seven storms between July 2001 and November 2002 and showed that the channel corridor (channel and ditch banks, and ditch beds) were significant sources averaging 76.5 % of the total sediment sources for the seven storms. Results indicate that sediment sources vary between events, and may be affected by seasonality and runoff conditions. Cropland was an important source of sediment for the two storms with the highest peak flow which occurred in the late summer and fall when harvesting began and vegetative cover was low. Ditch beds, which contributed an average of 46.1 % of sediment for the seven storms, were important sources of sediment over a range of peak flows (0.2 m 3 /s to 15.7 m 3 /s) and may also be important when crop areas have mature leaf cover.

Eos, Transactions American Geophysical Union, 1985

Index terms are those keywords attached to journal articles and geophysical abstracts in press (G... more Index terms are those keywords attached to journal articles and geophysical abstracts in press (GAP) that facilitate their categorization and consequently allow for rapid searches of the published literature by topical areas. AGU published an index set in 1973 that became a standard in the geophysical sciences in that other organizations also incorporated this set into their index schemes.

Open-file report /, 1998

The U.S. Geological Survey has been cooperating with other scientists under the auspices of the I... more The U.S. Geological Survey has been cooperating with other scientists under the auspices of the Interstate Commission on the Potomac River Basin to utilize existing data from the tidal Potomac River and Estuary for investigating linkages among living resources (primary producers, consumers) and abiotic components of the environment. Because the distribution and abundance of submersed aquatic vegetation in the tidal Potomac River and Estuary are controlled largely by light availability, the first step in investigating linkages with submersed aquatic vegetation is to examine the correlations that exist among vegetative cover, discharge, water quality and weather, all of which can affect light availability directly or indirectly. Growing season (April-October), spring (April-June), and summer (July-August) correlations are presented along with figures demonstrating the significant relationships among variables. INTRODUCTION The ecosystem of the Chesapeake Bay, the Nation's largest estuary, has been adversely affected during the past several decades by eutrophication caused by excessive nutrients entering the bay. Nutrient loading has been identified as the primary cause of periods of hypoxia that kill or stress living resources in parts of the bay. Additionally, high nutrient and sediment loads have decreased water clarity and consequently are largely responsible for the decline in submersed aquatic vegetation (SAV) that form the base of the food chain and provide critical habitat for finfish, shellfish, and waterfowl. The mission of the U.S. Geological Survey's (USGS) Chesapeake Bay Ecosystem Program is to provide information to a broad community of policy makers, resource managers, scientists, and private citizens working on the restoration of the Chesapeake Bay. As part of this mission, USGS scientists collect and analyze data on current and historical nutrient and sediment loads in the drainage basin of the Chesapeake Bay and determine linkages between hydrologic parameters and the distribution and abundance of SAV in the Potomac River drainage basin. Light is the primary factor controlling the distribution and abundance of SAV in the Chesapeake Bay and its tributaries (Batiuk and others, 1992; Carter and others, 1994; Carter and Rybicki, 1990). Light availability for SAV photosynthesis and growth is affected by water-column components such as total suspended solids (TSS) and chlorophyll-a (Carter and Rybicki, 1990). Additionally, epiphytic growths on the leaves and stems of SAV further reduce light availability for photosynthesis. Eutrophication causes an increase in the abundance of phytoplankton and thus increases chlorophyll-a, TSS, and epiphyte loads. Weather (precipitation, windspeed, available sunshine) also affects the amount of light available for photosynthesis and thus the distribution and abundance of SAV (Carter and others, 1994). The USGS is cooperating with other scientists under the auspices of the Interstate Commission on the Potomac River Basin (ICPRB) to utilize existing data from the tidal Potomac River and Estuary for investigation of linkages among primary producers, consumers, water-quality and weather parameters, and discharge.

Limnology and Oceanography, May 1, 2007

We assessed species-specific coverage (km 2) of a submerged aquatic vegetation (SAV) community in... more We assessed species-specific coverage (km 2) of a submerged aquatic vegetation (SAV) community in the fresh and upper oligohaline Potomac Estuary from 1985 to 2001 using a method combining field observations of species-proportional coverage data with congruent remotely sensed coverage and density (percent canopy cover) data. Biomass (estimated by density-weighted coverage) of individual species was calculated. Under improving water quality conditions, exotic SAV species did not displace native SAV; rather, the percent of natives increased over time. While coverage-based diversity did fluctuate and increased, richness-based community turnover rates were not significantly different from zero. SAV diversity was negatively related to nitrogen concentration. Differences in functional traits, such as reproductive potential, between the dominant native and exotic species may explain some interannual patterns in SAV. Biomass of native, as well as exotic, SAV species varied with factors affecting water column light attenuation. We also show a positive response by a higher trophic level, waterfowl, to SAV communities dominated by exotic SAV from 1959 to 2001.

Water Resources Research, Jun 1, 1978

The geometric mean is often used to express acceptable levels of fecal coliform counts in federal... more The geometric mean is often used to express acceptable levels of fecal coliform counts in federal and state water quality criteria or standards. The expected value of the geometric mean is shown to be a function of the sample size and to be very sensitive to the skew as well as to the form of the underlying distribution function. Implications of these findings are discussed with regard to standards. In particular, it is noted that great care must be taken in specifying the minimal sample size to be used. 'Not to exceed a median fecal coliform bacterial concentration of 14 MPN per 100 ml with not more than 10 percent of samples exceeding 43 MPN per 100 ml for taking of shellfish.' These criteria can be contrasted with the report of the National Academy of Sciences, National Academy of Engineering [1972] 'Water Quality Criteria 1972,' in which 'no specific recommendation is made concerning the presence or concentrations of microorganisms in bathing water,' but 'it is recommended that the geometric means of fecal coliform and total coliform densities in raw surface water sources (for public supply) not exceed 2,000/100 ml and 20,000/100 ml, respectir•ely. ' Furthermore, with regard to the harvesting of shellfish the National Academy of Sciences and the National Academy of Engineering recommended that the water quality meet the National Shellfish Sanitation Standards, which require that 'the coliform median most probable number (MPN) of the water does not exceed 70 per 100 ml, and not more than 10 per This paper is not subject to U.S. copyright. Published in 1978 by the American Geophysical Union. cent of the samples ordinarily exceed an MPN of 230 per 100 ml for a five-tube decimal dilution test .... '

Geophysical Research Letters, Nov 13, 2008

With a new automated precipitation collector we measured a remarkable decrease of 51% in the hydr... more With a new automated precipitation collector we measured a remarkable decrease of 51% in the hydrogen isotope ratio (d 2 H) of precipitation over a 60-minute period during the landfall of an extratropical cyclone along the California coast on 21 March 2005. The rapid drop in d 2 H occurred as precipitation generation transitioned from a shallow to a much deeper cloud layer, in accord with synoptic-scale ascent and deep ''seeder-feeder'' precipitation. Such unexpected d 2 H variations can substantially impact widely used isotope-hydrograph methods. From extreme d 2 H values of À26 and À78%, we calculate precipitation temperatures of 9.7 and À4.2°C using an adiabatic condensation isotope model, in good agreement with temperatures estimated from surface observations and radar data. This model indicates that 60 percent of the moisture was precipitated during ascent as temperature decreased from 15°C at the ocean surface to À4°C above the measurement site.

Water Resources Research, Oct 1, 1979

Distributions whose inverse forms are explicitly defined, such as Tukey's lambda, may present pro... more Distributions whose inverse forms are explicitly defined, such as Tukey's lambda, may present problems in deriving their parameters by more conventional means. Probability weighted moments are introduced and shown to be potentially useful in expressing the parameters of these distributions.

... if these results are unduly influenced by the small sample sizes available to us for some sys... more ... if these results are unduly influenced by the small sample sizes available to us for some systems, in particular during El Nino or La ... gov/nasqan/ [2] COPLEN, T., KENDALL, C., Stable hydrogen and oxygen isotope ratios for selected sites of the US Geological Survey's NASQAN ...

Science, Oct 9, 1992

(1990), p. 31 describes the San Andreas fault as a system of several major fault zones. Each comp... more (1990), p. 31 describes the San Andreas fault as a system of several major fault zones. Each comprises numerous fault segments consisting of individual faults. Geological segments are typically recognized by their geometry, but segments can be defined by their seismic rupture properties or by other geophysical characteristics common to contiguous faults of a fault zone. In (7 I) fault zones are defined in terms of contiguous straight fault segments, some of which were used in the present study. We did not consider segments smaller in length than the plate thickness (=I0 km), and we treated the Hayward, Calaveras, and San Gregorio faults as zones of groups of segments.

Quaternary Research, Sep 1, 1997

, dated using alpha-spectromet-Reanalysis and additional dating of the Devils Hole d 18 O paleori... more , dated using alpha-spectromet-Reanalysis and additional dating of the Devils Hole d 18 O paleoric (AS) uranium-series methodology. More recently, a 36temperature record confirm that the last interglaciation in the cm-long core of vein calcite from Devils Hole, dated using Great Basin (the continental analog of marine isotopic substage thermal-ionization mass-spectrometric (TIMS) uranium-se-5e) lasted Ç22,000 yr, consistent with the Vostok paleotemperaries methodology (Ludwig et al., 1992), indicated that not ture record which suggests a duration of Ç19,000 yr for this event only the last interglaciation, but also the three interglaciain Antarctica. The three preceding interglaciations in the Devils tions preceding it, lasted Ç20,000 yr or longer (Winograd Hole record (analogs of marine isotopic substages 7e, 9c, and 11c) et al., 1992). range from 20,000 to 26,000 yr in duration. A Ç20,000-yr duration Whether past interglaciations lasted on the order of 10,000 for the last interglaciation is consistent with TIMS uranium-series yr, as indicated by marine d 18 O records, or twice as long, as dated sea-level high stands. Thus, the widely held view that intersuggested by continental stable isotopic paleotemperature glaciations were of 11,000-to 13,000-yr duration and constituted only about 10% of mid-to-late Pleistocene climatic cycles needs records (i.e., Vostok and Devils Hole), is mandatory backreexamination. The warmest portion of each interglaciation in the ground information in evaluating the likely duration of our Devils Hole time series is marked by a d 18 O plateau, signifying present interglacial climate and the magnitude of anthropoapparent climatic stability for periods of 10,000-to 15,000-yr duragenic alterations to it. Examination of evidence bearing on tion. ᭧ 1997 University of Washington. the validity of these divergent opinions is the first goal of this study. Discerning patterns in the structure of past interglaciations that might provide clues pertinent to the duration 141

Quaternary Research, Sep 1, 2006

The mid-to-late Pleistocene Devils Hole δ18O record has been extended from 60,000 to 4500 yr ago.... more The mid-to-late Pleistocene Devils Hole δ18O record has been extended from 60,000 to 4500 yr ago. The new δ18O time series, in conjunction with the one previously published, is shown to be a proxy of Pacific Ocean sea surface temperature (SST) off the coast of California. During marine oxygen isotope stages (MIS) 2 and 6, the Devil Hole and SST time series exhibit a steady warming that began 5000 to > 10,000 yr prior to the last and penultimate deglaciations. Several possible proximate causes for this early warming are evaluated. The magnitude of the peak δ18O or SST during the last interglacial (LIG) is significantly greater (1 per mill and 2 to 3°C, respectively) than the peak value of these parameters for the Holocene; in contrast, benthic δ18O records of ice volume show only a few tenths per mill difference in the peak value for these interglacials. Statistical analysis provides an estimate of the large shared information (variation) between the Devils Hole and Eastern Pacific SST time series from ∼ 41 to ∼ 2°N and enforces the concept of a common forcing among all of these records. The extended Devils Hole record adds to evidence of the importance of uplands bordering the eastern Pacific as a source of archives for reconstructing Pacific climate variability.

Eos, Transactions American Geophysical Union, 2001

Water science finds itself at an interesting and critical crossroads. Sophisticated atmospheric m... more Water science finds itself at an interesting and critical crossroads. Sophisticated atmospheric modeling, remote sensing, and Internet‐based exchange of data enable exciting new synergies to develop among scientists, policy‐makers, and the private sector. Paradoxically we find it evermore difficult to validate products from these high‐technology tools and to exploit their full potential due to a severe and sustained decline in available hydrologic data sets.