Journal of Environmental Quality 31:6-16 (2002)
© 2002 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
SPECIAL SUBMISSIONS
Findings from the USDA-sponsored Lake Erie Agricultural Systems for Environmental Quality Project
The Lake Erie Agricultural Systems for Environmental Quality Project
An Introduction
R. Peter Richards*,a,
Frank G. Calhounb and
Gerald Matisoffc
a Water Quality Laboratory, Heidelberg College, 310 E. Market Street, Tiffin, OH 44883
b School of Natural Resources, The Ohio State University, Columbus, OH 43210
c Department of Geological Sciences, Case Western Reserve University, Cleveland, OH 44106
* Corresponding author (prichard{at}heidelberg.edu)
| Findings from the USDA-sponsored Lake Erie Agricultural Systems for Environmental Quality project that examinded the relationships between agricultural land use and water quality in northwestern Ohio from 1975 through 1995. Special Editor was Dave Eckhardt.
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Received for publication August 12, 2000.
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ABSTRACT
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In the last part of the twentieth century, recognition became widespread of the important effect of agricultural runoff on the health of aquatic ecosystems in the Lake Erie basin and elsewhere. Because of the efforts to remediate Lake Erie, the "dead lake" among the Laurentian Great Lakes, a number of research and demonstration projects were undertaken in the Lake Erie basin to evaluate and foster adoption of conservation tillage and other farming techniques that would reduce runoff while maintaining productivity. In addition, intensive water quality studies of long duration were begun on major tributaries to Lake Erie during this time. The Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) project examined governmental programs, changes in agriculture, and changes in water and soil quality during the period 1975–1995, and sought to evaluate the linkages among these factors. The study area is characterized by extensive agricultural land use of soils developed from glacial materials deposited on Paleozoic sedimentary bedrock, mostly limestone. Tile drainage is extensive, particularly in slow-draining clay-rich lacustrine soils in the lower reaches of the watersheds. This paper introduces the study area, its geology, geography, soils, and agricultural history. In addition, we provide an overview of the LEASEQ concept and introduce the 11 other papers in this series, which provide a detailed exposition of the results of our studies.
Abbreviations: LEASEQ, Lake Erie Agricultural Systems for Environmental Quality
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INTRODUCTION
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IN THE 1960S AND EARLY 1970S, Lake Erie was frequently referred to as a "dead lake". Excessive phosphorus loading was identified as a major cause of the eutrophication of Lake Erie. In the Army Corps of Engineers' Lake Erie Wastewater Management Study, an interdisciplinary team was established to identify phosphorus sources and develop plans to reduce phosphorus loading. The first line of attack was to reduce loadings from point sources discharging directly to the lake. Upstream point sources and agricultural lands were identified as additional phosphorus sources from which loadings would need to be reduced. Through demonstration projects, conservation tillage was identified as the most cost-effective means to reduce phosphorus loading from agricultural lands. Beginning in the early 1970s, several major programs were implemented to foster basinwide adoption of conservation tillage, as well as other practices to reduce erosion and the transport of sediment and particulate phosphorus into Lake Erie. These programs, and other economic influences, have brought about major changes in agricultural management practices.
The Water Quality Laboratory at Heidelberg College has been monitoring water quality near the mouths of the two largest U.S. tributaries to Lake Erie, the Maumee and Sandusky Rivers, since 1969, with daily and more frequent samples. The resulting data sets are the longest-term and most detailed available in the United States to reflect water quality in rivers draining land dominated by agriculture, and are ideally suited to support a study of water quality responses to changing agricultural practices. In addition, a soils archive is available at The Ohio State University that allows examination of changes in the quality of the soil resource during this time.
The Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) project was conceived as a retrospective examination of the effect of these governmental programs and other changes in agriculture, and their influence on water and soil quality and agricultural outputs. The study area (Fig. 1)
comprises the watersheds of the Maumee and Sandusky Rivers, the two largest U.S. tributaries of Lake Erie. The study area is located mostly in northwestern Ohio but includes portions of northeast Indiana and southern Michigan. The maps included in this paper in most cases display data to the edges of the counties indicated in Fig. 1, but our discussions in this paper, and in several that follow, are generally limited to the portions of these counties that lie within the Maumee and Sandusky watersheds, because the study area is defined by watershed boundaries, not county boundaries.
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Fig. 1. The Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) study area includes the watersheds of the Maumee and Sandusky Rivers (shaded), located in northwestern Ohio, northeastern Indiana, and southern Michigan. The circles near the mouths of the rivers indicate the locations of the Water Quality Laboratory sampling stations, at Woodville on the Maumee and at Fremont on the Sandusky. The scale for this map applies also to Figures 2, 3, and 5 through 8.
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Fig. 2. Bedrock geology of the Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) study area, based on maps obtained from web sites of the Ohio, Indiana, and Michigan Geological Surveys.
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Fig. 3. Surficial geology of the Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) study area, based on maps obtained from web sites of the Ohio, Indiana, and Michigan Geological Surveys.
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Fig. 5. Physiographic regions of the Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) study area. Based on the Ohio map of Brockman (1998) and the Indiana map of Gray (2000), with reasonable extrapolations into Michigan based on geographic trends and on the Michigan Level III ecosystem map. Unit names shown in the legend are applicable to Ohio only.
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Fig. 8. Anderson Level I land use classification of the Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) study area. Land use from U.S. Geological Survey Geographic Information Retrieval System data, 1990, scale 1:250000.
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The LEASEQ team consists of researchers from Case Western Reserve University, Heidelberg College, and The Ohio State University. In the series of 11 papers that follow, we present our findings from this study of an evolving agricultural ecosystem. The purpose of this paper is to provide overviews of the study area, the LEASEQ concept, and the remaining papers in this series.
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GEOLOGY AND GEOGRAPHY
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The bedrock geology of the study region (Fig. 2)
consists mostly of Silurian and Devonian limestones and dolomites situated on the northward plunging Cincinnati–Findlay Arch. During the 250 million years between deposition of these Paleozoic sediments and the first glacial advance, an extensive river system developed. In the southern portion of Ohio, the Pleistocene Teays River drained westward into the preglacial Mississippi River, and in the northern portion of Ohio and in what is now Lake Erie, the drainage was to the east along the ancestral St. Lawrence River valley (Spenser, 1891; cited by Herdendorf, 1988). The Pleistocene glaciers followed the preglacial valleys and scoured them deeper and wider. As the ice sheets paused in their advance or retreat, deposition of rock debris (till) at the ice margins resulted in the formation of end moraines (Fig. 3)
, which dammed the natural drainage and created large lakes in the scoured depressions. Approximately 14000 years ago the northward retreat of the ice created the first recognized ice-dammed lake, Lake Maumee (Fig. 4)
, at an elevation of 244 m (800 ft) (Forsyth, 1971). Lake Maumee drained to the west near Fort Wayne, Indiana. Over the next 5000 years, lake levels fluctuated greatly, as different lake outlets to the west and east were exposed or sealed by the ice and as the land rose isostatically by glacial rebound following retreat of the ice (Fig. 4). About 16 different lake levels have been identified, from the highest level of Lake Maumee (244 m or 800 ft) to the lowest level of Lake Erie (137 m or 450 ft), based on the presence of beach ridges and other beach deposits. By approximately 9000 years before present (BP), the shoreline of Lake Erie was similar to the present. A more detailed description of the post-glacial history of Lake Erie can be found in Barnett (1992).
Current soils reflect the origin of the sediment (beach ridges, lake plain, till plain, end moraine) that was deposited during the glacial retreat. The physiographic regions of the study area (Brockman, 1998; Gray, 2000) reflect a combination of the glacial geology, bedrock geology, topography, soils, and geologic history. This can be seen in a comparison of the glacial map (Fig. 3) with the physiographic map (Fig. 5)
. The "Black Swamp" occupied the Maumee Lake Plains (Region 7). This area consisted of saturated soils with some trees and shrubs, and occasional well-drained, oak-covered higher ground, that formed from beach ridges, dunes, bars, and deltas of ancestral Lake Erie (Region 7.2, the Maumee Sand Plains). The low, wet areas were clay flats of the deepest part of the lake basin (Region 7.1, the Paulding Clay Basin). This is Ohio's flattest area; the difference in elevation between the highest swell and the lowest swale is less than 5 feet (approximately 1.5 m).
Detailed physiographic interpretations have been combined with ecological information to characterize areas of similar ecology, called ecoregions (Omernik, 1987). Level IV ecoregions for the LEASEQ study area (Woods et al., 1998) are presented in Fig. 6 . The similarity of these ecoregions to the physiographic regions of Fig. 5 is readily apparent. The major ecoregions that comprise the LEASEQ study area are the Huron–Erie Lake Plains (Ecoregion 57) and the Eastern Corn Belt Plains (Ecoregion 55), described as follows (Woods et al., 1998):
"Ecoregion 57 is a broad, fertile, nearly flat plain punctuated by relict sand dunes, beach ridges, and end moraines. Originally, soil drainage was typically poorer than in Ecoregion 55 and elm–ash swamp and beech forests were dominant. Oak savanna was typically restricted to sandy, well-drained dunes and beach ridges. Today, most of the area has been cleared and artificially drained and contains highly productive farms producing corn, soybeans, livestock, and vegetables; urban and industrial areas are also extensive. Stream habitat and quality have been degraded by channelization, ditching, and agricultural activities.
"Ecoregion 55 is primarily a rolling till plain with local end moraines. It has lighter colored soils than Ecoregion 54 [to the west in Illinois], loamier and better-drained soils than Ecoregion 57, and richer soils than Ecoregion 61 [to the east]. Glacial deposits of Wisconsinan age are extensive; they are not as dissected nor as leached as the pre-Wisconsinan till, which is restricted to the southern part of Ecoregion 55. Originally, natural tree cover was greater than Ecoregion 54; beech forests were common on Wisconsinan soils while beech forests and elm–ash swamp forests dominated the wetter pre-Wisconsinan soils. Today, extensive corn, soybean, and livestock production occurs and has affected stream chemistry and turbidity."
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SOILS
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Both the Maumee and Sandusky watersheds have headwaters that originate in a combination of glacial till plains (ground moraines) and end moraines (ridge moraines). The downstream part of each watershed is composed of lacustrine materials, glacial till, and beach sand. The headwater areas of both are characterized by rolling topography with greatest slopes in the end moraines. It is often assumed that the downstream, topographically flat parts of the basins consist of uniform lacustrine clays. In fact, there is considerable variability in particle size distribution that is not always reflected in landscape breaks. These lacustrine sediments, in varying thicknesses and textures, rest on glacial till. If there is a texture contrast across these lacustrine–till contacts, the contrast represents a significant change in hydraulic conductivity affecting both subsurface and surface water flow. Such areas are spatially defined by soils maps.
Original vegetation in both watersheds was mostly swamp forest and sedges on the lake plain and hardwood forest and pockets of prairie in the moraine areas. More than 85% of the original forest has been cleared for agriculture and other development. Tile drainage is used extensively throughout the lake plain region and use is expanding in the moraines. The parent materials have high contents of weatherable minerals and the soils are less than 15000 years old.
Because of the difficulty of integrating soils maps across state lines, the discussion that follows is limited to the Ohio portion of the study area. Of the 480 recognized soil series in Ohio, 130 occur in northwestern Ohio. Three general soil associations (Fig. 7)
comprise almost the entire study area and these are closely related to parent materials and physiography (Fig. 2, 3, and 5).
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Fig. 7. General soils of the Ohio portion of the Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) study area.
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Soils on Moraines
The Bennington (fine, illitic, mesic Aeric Epiaqualfs)–Cardington (fine, illitic, mesic Aquic Hapludalfs)–Centerburg (fine-loamy, mixed, active, mesic Aquic Hapludalfs) association occupies the southeastern and central parts of the Sandusky River watershed. This association is composed of very deep soils formed in loamy till of medium calcium carbonate content (8–22% in the C horizon). The soils occur on ground moraines and end moraines, and are typically silt loam and less commonly loam or fine sandy loam with very strongly acid to neutral pH. This soil association reflects the increased proportion of sandstones and shales incorporated into the glacial deposits from west to east across Ohio. A small area of soils derived from low-carbonate till (1–8%) occurs in the extreme southeastern corner of the Sandusky River watershed.
The Blount (fine, illitic, mesic Aeric Epiaqualfs)–Glynwood (fine, illitic, mesic Aquic Hapludalfs)–Pewamo (fine, mixed, active, mesic Typic Argiaquolls) association dominates the headwater areas of both watersheds. This association is composed of very deep soils formed in loamy till of high lime content (22–35%) with a thin layer of loess in some areas. As a group they form a catena (landscape association) and account for 33% of the total area of the two watersheds. Pewamo has an A horizon that is 25 to 45 cm thick and has an organic matter content of 2 to 8%.
Soils on Lake Plains
The Hoytville (fine, illitic, mesic Mollic Epiaqualfs)–Nappanee (fine, illitic, mesic Aeric Epiaqualfs)–Paulding (very-fine, illitic, nonacid, mesic Typic Epiaquepts)–Toledo (fine, illitic, nonacid, mesic Mollic Endoaquepts) association represents two separate groups of soils that occur on lake plains but differ in mode of deposition and, consequently, particle size distribution.
Hoytville and Nappanee soils occupy 19% of the Maumee and Sandusky basins. They formed in glacial till that had been leveled by wave action. The Ap horizon is typically clay, clay loam, and silt loam. Calcium carbonate equivalent in the C horizon ranges from 15 to 30 percent. Both series have an argillic horizon as a result of clay movement from the A horizon downward to the Bt horizon. Hoytville soils have thicker A horizons and more organic matter than do the Nappanee soils.
Paulding and Toledo soils occupy 6% of the two watersheds. They are very deep, very poorly drained soils formed in clayey lacustrine sediments. The Paulding is higher in clay than the Toledo. Paulding soils have Ap horizons that are less thick and lower in organic matter than the Toledo series. Toledo soils have a corn yield rating 33% greater than Paulding (Soil Survey Staff, 1997).
Other Soils
The 10 soil series described above account for more than 50% of the combined land area of the two watersheds. The remaining 50% of the basins are composed of soils found on floodplains, outwash plains, beach ridges, deltas, dunes, and other landforms. They are locally important but not extensive enough to be shown at the scale used in Fig. 7.
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LAND USE HISTORY
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Land Clearing and Initial Agriculture
The progression of land clearing and early agriculture in northwestern Ohio occurred at a different pace in the moraine areas than in the lake plains. The moraine and beach ridge areas of the basins were settled and cleared for agricultural production well before the lake plain region. The lake plain region in the Maumee watershed was known as the "Great Black Swamp" and was initially avoided due to mosquito-borne typhoid and malaria. Initial clearing, by hand, of the upland areas began shortly after the Revolutionary War with the signing of the Greenville Treaty of 1795 in which Indian tribes ceded large portions of their land (Jones, 1983). By 1860 more than 60% of the state was in "improved" farmland; this increased to 74% by 1880. The counties that were predominantly in the lake plain in the northwest were still well below 60% improved in 1880 because of drainage problems. By 1850 the "pioneer era" was complete as the horse-drawn moldboard plow was widely adopted. The end of the Civil War brought significant changes to the agriculture of northwestern Ohio. Equipment such as improved grain harvesters, cultivators, and small-grain seeders were introduced and widely adopted by 1870. There was a rapid transfer from hand power to horses between 1862 and 1875 (Economic Research Service, 1992). By 1920 tractors were starting to replace horses, with the changeover largely complete by 1945. Gang plows became more common with the switch to tractors. Average plow depth was around 15 cm in the 1950s and by the 1980s it had increased to 25 cm.
As soil organic matter declined, crop rotations that included legumes such as clover (Trifolium spp.) or alfalfa (Medicago sativa L.) became common in the first decades of the 20th century. This practice seems to have been common into the 1950s but then declined due to low energy and fertilizer costs. Also, herbicides, insecticides, and hybrid varieties of corn (Zea mays L.), wheat (Triticum aestivum L.), and oat (Avena sativa L.) led to the sharp decline of grain-legume rotations. The primary selling point for these rotations was disease–weed control and organic matter maintenance. As late as 1920, chemical fertilizers were still not used extensively in northwestern Ohio. From 1820 to 1900, crop residues were usually burned and animal manure was treated as a nuisance (Wilhelm, 1983). Commercial fertilizer use was much higher in some counties than others. In 1890, Wood County used 58 metric tons on 64000 hectares while Henry County used only 3 metric tons on 42000 hectares in the same year.
Tile Drainage
Most of the following discussion on the drainage of the lake plains is based upon Wilhelm (1983). Drainage was the key to agricultural development of the lake plains of northwestern Ohio. The initial step was to provide surface drainage. In 1859 the State of Ohio enacted the "Ditch Law", which authorized construction of open surface ditches through petition to the local government by landowners. Most of the open surface ditches in the lake plain were constructed between 1870 and 1920. By 1920 there were more than 24000 km of open drains in northwestern Ohio that had "improved" nearly 2000000 ha of land.
Tile drainage or "underdrainage" was practiced by the Romans in the second century BC. French farmers used buried horseshoe-shaped roof tile for subsurface drainage in the 14th and 15th centuries. By the 1860s local farmers in the lake plains were using the available lumber from clearing the swamp to create plank "underdrains. These wooden underdrains were considered to be temporary measures until the tile kilns arrived. Most predictions were that they would last 10 to 15 years. In the 1930s and 1940s ditching machine operators found that many of these plank drains were still functioning properly after as much as 80 years.
Most of the clearing of the land was accomplished between 1860 and 1885. A beneficial side effect of the clearing was that as the tree stumps and taproots decayed they left channels that provided an effective water conduit for many years. Tile kilns were replacing the sawmills by 1880. Although tile kilns were common in central Ohio by 1860 the cost to haul tiles over 300 km to northwestern Ohio was prohibitive. The clay for local manufacture of tiles came from the lake plain soils.
The ditches for the tile were dug and the tile laid by hand for more than 20 years, with a short intervening attempt to use horsepower, which proved unsatisfactory. It was only after the turn of the century that a steam-driven, mechanical trencher finally replaced hand labor. Presently, there are more than 400000 km of drain tile in northwestern Ohio. The majority of it is in what was referred to as the Great Black Swamp, an area roughly 65 by 200 km in size. An unknown but certainly high percentage of this tile was installed by hand.
By 1983 there were only two clay drain tile manufacturers remaining in northwestern Ohio after plastic drain tubing was introduced in 1967. At a 1995 cost of about $0.50 per foot ($1.65 per meter) (Duvick, 1996), the ditching and installation of perforated, corrugated drainage tubing has encouraged extensive renovation of existing clay-tiled fields in northwestern Ohio.
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CURRENT LAND USE
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An Anderson Level I (Anderson et al., 1976) land use map for the study area is shown in Fig. 8
. Agricultural land use is dominant, comprising more than 85% of the Maumee and Sandusky watersheds. Forested lands comprise about 8% of the watershed and are distributed fairly uniformly through the two basins; major areas of continuous forest are lacking. Much of the forest land consists of woodlots located in the center portions of one-mile-square sections, occupying the areas farthest from the roads that bound these sections. Three major urban areas are located in the Maumee basin: Toledo adjacent to Maumee Bay in Lake Erie, Fort Wayne at the western boundary of the watershed in Indiana, and Lima near the southern boundary of the watershed in Ohio. The Toledo urban area is located downstream from the water quality sampling station on the Maumee, and is therefore not included in analyses presented in the remaining papers in this series. A number of smaller cities and towns are scattered throughout the two watersheds.
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THE LEASEQ CONCEPT
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The LEASEQ study area can be thought of as a landscape-level agroecosystem that is evolving through time (Fig. 9)
. The soils of Lake Erie watersheds make up the resource base of the agroecosystem. One type of input to the system is the various management practices used by farmers, such as the amounts, timing, and placement of fertilizer, pesticide use, and tillage practices. Weather conditions are another type of input to the system. Outputs from the system include agricultural products, most of which are exported from the system, but some of which are recycled back into the system as animal feed. Water quality is viewed as an output of the system and is reflected in the concentrations of sediments, nutrients, and pesticides in the stream systems and the loads of these chemicals exported to Lake Erie.
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Fig. 9. A conceptual framework for the Lake Erie Agricultural Systems for Environmental Quality (LEASEQ) study: An agricultural ecosystem evolving over time.
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The quality of the soil resource has a profound influence on the productivity and "health" of the agroecosystem. Long-term modifications in management practices create changes in fundamental soil properties, such as organic carbon content, cation exchange capacity, water retention characteristics, temperature, and aggregate stability. These alterations have, in turn, an effect on other system outputs, including water quality and agricultural production.
During and even before the 20-year study period (1975–1995), a series of agricultural pollution abatement programs sought to improve water quality by bringing about voluntary changes in the selection of agricultural management practices used by area farmers. A variety of incentives has been used to influence farmer choices of management practices. Farmers' decisions on management practices are also influenced by a wide variety of other factors, including the economy, technological innovations, and demographic patterns, some of which have also changed during the past 20 years. Climate change may have also occurred during the past 20 years in ways that could introduce trends in water quality. In Fig. 9, these agents of change are referred to as forcing factors.
The general goal of the LEASEQ program is to examine the history of the compartments shown in Fig. 9, determine how each has changed, and attempt to relate changes in outputs and the soil resource base itself to changes in inputs and forcing factors. Of particular interest is the question of whether changes in agricultural management practices have had beneficial effects on the various outputs of the agroecosystem. The series of papers that follow reports various aspects of our findings.
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OVERVIEW OF THE LEASEQ PAPERS
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The relationships between agricultural management practices and governmental programs that seek to change the practices in order to reduce nonpoint pollution are complex. Because participation is generally voluntary, the approach is often built strongly on education and the use of incentive payments, but political and other practical influences often interfere with what might be the scientifically optimal distribution of effort. What governmental programs were implemented during the latter part of the 20th century within the study area? What were their goals? How successful were they in meeting these goals? How cost effective were they? These questions are investigated in the paper by Forster and Rausch (2002). Partly as a consequence of these government programs, farmers have adopted conservation practices that affect Lake Erie basin water quality. At the same time, these practices also had economic effects, such as changing net farm income and farm size. Forster (2002) probes the data from longitudinal surveys of farmers' behavior and uses a farm-level simulation model to investigate economic impacts of changes in farming practices.
What changes have taken place in the agricultural land resource and its use that might be expected to affect water quality? Has the amount of farmland changed? What have been the patterns of fertilizer use? Have crop preferences changed? Have yields improved? These and similar questions are investigated in the paper on agricultural trends by Richards et al. (2002). What changes have occurred in the soil resource itself? Is soil quality different in 1995 than in 1975? Have soil phosphorus levels increased during this time? What is the relationship between soil phosphorus levels and fertilizer sales? Calhoun et al. (2002b) compare archived soil samples with contemporary samples from the same locations to investigate these questions. What do we know about the impact of soil properties on pollutant export from small watersheds? Is it valid to assume that sloping moraine areas are the primary source of pollutants? Calhoun et al. (2002a) examine previous water quality studies in order to resolve these questions. What rates of erosion are characteristic of agricultural land use? Are these rates of erosion for fields under conventional tillage different from those under conservation tillage? Matisoff et al. (2002a) employ a radioisotope inventory technique to investigate these questions.
If farmers are successful in reducing soil loss due to erosion during storm events, how long will it take for this improvement to become apparent in improved water quality? One important aspect of this issue is the question of how far sediment particles travel in individual storm runoff events, once they are delivered to the stream or river. This question is investigated by Matisoff et al. (2002b) using two independent approaches, one based on atmospherically derived radioisotopes, and the other based on kinematic wave theory.
The interaction of the land and water is strongly influenced by weather, especially rainfall. Weather-influenced variability hinders the evaluation of relationships between agricultural management practices and water quality. Systematic shifts in climate over a period of years have direct effects on the land resource, and may reinforce or counterbalance changes in water quality that result from changes in agricultural management practices, or may produce trends in water quality that have no relationship to management practices. Among the many available climatic variables, which are strongly correlated with measures of water quality? What trends are apparent in climatic variables during the study period? To what extent can these climate trends explain observed trends in water quality? These questions are investigated in two papers by Moog and Whiting (2002a)(b). The first paper examines the relationships between climatic variables and water quality parameters, the second analyzes the influence of trends in climate on trends in water quality.
Water quality trends and their possible relationship to changes in agricultural management are the central theme of the LEASEQ study, and this subject is addressed in three papers. How has water quality changed during the study period? Richards and Baker (2002) report the results of trend analyses for discharge, sediment, and four nutrient parameters in the Maumee and Sandusky River watersheds, and offer some observations on the relationships of these trends to agricultural practices. The influence of watershed size on the interaction of soils in the watershed and water quality at the watershed outlet is investigated in the paper by Calhoun et al. (2002a). In the final paper in our series, Baker and Richards (2002) apply an annual nutrient-budget approach to integrate phosphorus inputs and outputs to fields in the LEASEQ study area, and investigate whether the study area is characterized by a net import or export of phosphorus.
The LEASEQ project has documented important changes in agriculture and substantial improvements in water quality that we believe result from the observed changes in agricultural practices. Details are available in the following papers.
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ACKNOWLEDGMENTS
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Data for the maps in this paper were drawn from many sources, including some not yet generally available. We particularly thank Henry Gray, Scott Brockman, Kevin Kincare, Jeff Comstock, and Jim Omernik for sharing their specialized knowledge with us. Without their contributions the maps could not have been completed. We thank Dan Button of the Ohio Office of the USGS for providing the land use map. The tile drainage section relied heavily on the painstaking research done by Peter Wilhelm for his Masters thesis.
Support for the LEASEQ project was provided by a grant from USDA-CSREES. This support is gratefully acknowledged. Maury Horton has provided gentle and effective oversight as Project Officer. The Water Quality Lab acknowledges the many sources of support for the tributary monitoring program, which have allowed us to assemble the water quality datasets that form one of the core resources for this project. Among the most important sources of financial support have been the Army Corps of Engineers, the USEPA, and the State of Ohio. USEPA Region V and the Conservation Tillage Information Center provided generous partial support for the costs of publishing this set of papers. Flow data were provided by the USGS.
Finally, we acknowledge many fruitful conversations with members of the other Agricultural Systems for Environmental Quality projects.
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REFERENCES
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- Baker, D.B., and R.P. Richards. 2002. Phosphorus budgets and riverine phosphorus export in northwestern Ohio watersheds. J. Environ. Qual. 31:96–108 (this issue).[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
