Lorin K. Hatch

A review of research on the development of lake indices of biotic integrity.

Current methods of ecological health assessment of lakes within the United States are not adequate for meeting the requirements of the 1972 Clean Water Act (CWA) and assessing the condition of aquatic biota. Impairment status of lakes has typically been measured and classified by individual states via eutrophication standards or through the use of total maximum daily load (TMDL) protocols. These measurements often fail to account for effects of anthropogenic disturbances on aquatic biota that are not directly reflected by chemical and physical proxies of environmental condition. The index of biotic integrity (IBI) is a potentially effective ecological health assessment method that is meant to integrate ecological, functional, and structural aspects of aquatic systems. Furthermore, the IBI is meant to meet the requirements of the CWA by directly examining biological components of an ecosystem. The adaptation of the IBI for use in lake monitoring has increased in recent years as managers address the need to...

Daily phosphorus variation in a mountain stream

Monthly diel monitoring studies for phosphorus content were conducted (1995–1996 period) for multiple stations on Incline Creek, a mountain stream in the Lake Tahoe basin (California-Nevada). Large discharge and particulate P (PP) concentration fluctuations occurred during June in the early evening as snowmelt from higher elevations arrived at the lower stream reaches. June diel dissolved organic P (DOP) concentrations steadily increased, while soluble reactive P (SRP) concentrations remained constant. June diel PP concentrations associated with sand-sized particles (PPsand: >63 μm) exhibited a clockwise hysteresis, indicating possible sediment source depletion on a daily timescale. June diel PP associated with silt- and clay-sized particles (PPSC: >0.45 μm and <63 μm) exhibited counterclockwise hysteresis behavior, suggesting a potential groundwater contribution to PPSC. PPSC comprised the majority of PP concentration, except during high-discharge events when PPsand concentration was dominant. Areal PP loading, specifically PPsand, appears to originate primarily from the lower eastern branch of Incline Creek during the spring snowmelt season. Possible sources include a ski resort/parking lot and a golf course. DOP and SRP areal loads were greatest from the undeveloped upper subwatershed, suggesting that natural factors such as slope are influencing loading of small-sized P fractions.

Management of diffuse pollution in agricultural watersheds : Lessons from the Minnesota river basin

The Minnesota River (Minnesota, USA) receives large non-point source pollutant loads. Complex interactions between agricultural, state agency, environmental groups, and issues of scale make watershed management difficult. Subdividing the basins 12 major watersheds into agro-ecoregions based on soil type, geology, steepness, and climate enhances predictability of stream water quality parameters. An eight-step framework for agricultural watershed management is presented.

Stream Phosphorus Transport in the Lake Tahoe Basin, 1989–1996

Lake Tahoe is undergoing the initial stages of culturaleutrophication due to human alteration of the airshed andwatershed. The lakes switch from nitrogen (N) to phosphorus (P)limitation has been attributed primarily to atmospheric Nloading. This places an increased importance on controllingwatershed movement of P to the lake. A stream water qualitymonitoring data set consisting of nine streams in the Lake Tahoebasin has been analyzed to characterize the spatiotemporalvariation of P delivery to the lake. This data is from the LakeTahoe Interagency Monitoring Program (LTIMP), which providesscientific data for planning and regulatory agencies to addressenvironmental problems in the Lake Tahoe basin. Results indicatethat P delivery (concentrations, loads) varies greatly atinterannual, seasonal, and spatial scales. Annual and seasonaltotal P (TP) concentrations can vary up to three orders ofmagnitude in a given stream and are strongly associated withsuspended sediment. Particulate P is the major form of Ptransported by Tahoe streams and was strongly correlated withpercent surficial geologic deposits, which are primarily locatednear streams. Tahoe streams with the highest annualP concentrations often had the lowest annual P loads, and visaversa. P loading is greatest during the spring snowmelt (75% ofannual average). Potential watershed parameters influencing Pdelivery to Lake Tahoe have been identified as precipitation,basin area, basin steepness, and road and human developmentcoverage. Results also suggest that human development impacts onstream P loads are most prevalent during high precipitationyears. Identification and quantification of stream sediment andP sources such as streambanks and impervious surface isnecessary to aid in watershed restoration efforts.

Factors Affecting Iowa Lake and Reservoir Water Quality

ABSTRACT Iowa lake and reservoir water quality data collected during the summers of 1990 and 1992 were analyzed according to origin (lake vs. reservoir) and location, updating previous synoptic surveys. Morphometric comparisons between Iowa regions indicate unique characteristics for reservoirs, glacial lakes, oxbow lakes, and waterbodies on the Des Moines glacial lobe. All Iowa lakes and reservoirs are eutrophic although there is a significant range of water quality and within-region variability. Parameters such as chlorophyll a, total phosphorus (TP), and total nitrogen (TN) summer mean concentrations were highest on the Des Moines glacial lobe (means of 64 μg L−1, 164 μg L−1, and 4.4 mg L−1, respectively). A comparison of northern Iowa versus southern Minnesota lakes and southern Iowa versus northern Missouri reservoirs indicated that Iowa water quality is more eutrophic in both instances. Northern Iowa lakes had higher TN (3.0 mg L−1), total suspended solids (TSS, 39 mg L−1), and non-volatile suspended solids (NVSS, 18 mg L−1) summer mean concentrations than southern Minnesota lakes (2.1 mg L−1, 14 mg L−1, and 3 mg L−1, respectively). Southern Iowa reservoirs had higher TP (149 μg L−1), TN (1.8 mg L−1), TSS (34 mg L−1), and NVSS (25 mg L−1) summer mean concentrations than northern Missouri reservoirs (47 μg L−1, 0.7 mg L−1, 10 mg L−1, and 7 mg L−1, respectively).

Between- and within-lake responses of macrophyte richness metrics to shoreline development

Abstract Aquatic habitat in littoral environments can be affected by residential development of shoreline areas. We evaluated the relationship between macrophyte richness metrics and shoreline development to quantify indicator response at 2 spatial scales for Minnesota lakes. First, the response of total, submersed, and sensitive species to shoreline development was evaluated within lakes to quantify macrophyte response as a function of distance to the nearest dock. Within-lake analyses using generalized linear mixed models focused on 3 lakes of comparable size with a minimal influence of watershed land use. Survey points farther from docks had higher total species richness and presence of species sensitive to disturbance. Second, between-lake effects of shoreline development on total, submersed, emergent-floating, and sensitive species were evaluated for 1444 lakes. Generalized linear models were developed for all lakes and stratified subsets to control for lake depth and watershed land use. Between-lake analyses indicated a clear response of macrophyte richness metrics to increasing shoreline development, such that fewer emergent-floating and sensitive species were correlated with increasing density of docks. These trends were particularly evident for deeper lakes with lower watershed development. Our results provide further evidence that shoreline development is associated with degraded aquatic habitat, particularly by illustrating the response of macrophyte richness metrics across multiple lake types and different spatial scales.