Alberta is graced with a wonderful variety of lakes-perhaps as many different types as in any other region in the country. Within Alberta, clear lakes with sandy beaches decorate the Lakeland Region, warm green shallow lakes dot the prairie and parkland, brown water lakes occur throughout the Boreal forest, and pristine, cold, mountain lakes reflect spectacular scenery. We have added to this variety by creating new lakes, called reservoirs, in the southern half of the province. But particular kinds of lakes are not limited to one area. Lakes that are deep or shallow, green or clear, salty or fresh, may be found in many parts of the province.

Our natural lakes are very young from a geological perspective - most have been in existence no more than 12,000 years. With the retreat of the glaciers, numerous depressions and blocked waterways remained, which filled with water to form the vast array of lakes we see today. Alberta's lakes reflect not only its physical features, but also its climate. Where water is abundant, lakes abound - as in the vast region around Lake Athabasca, and in the Lakeland Region northeast of the city of Edmonton. The arid southeastern part of the province has few natural lakes. There is a surplus of water in the mountains, but much of it runs off to form rivers that flow across the province to the north or east. In the central part of the province between the arid south and the wet north, and in the Peace Country along the west-central edge of Alberta, are parkland and forest dotted with lakes of every size and description. All of these areas, except for the far northwest, are represented by lakes in the Atlas (Fig. 1). These lakes are shown on the map as part of the drainage basins of the largest rivers. Within the book, lake descriptions are organized by river basin, because with few exceptions lakes ultimately drain into rivers.

Four major rivers drain most of the province. The Peace and Athabasca rivers drain the northern half of Alberta. Their waters join with water from Lake Athabasca to form Alberta's largest river, the Slave River, which flows into the Northwest Territories and on to the Arctic Ocean. The North Saskatchewan River winds through the foothills and parkland of central Alberta. The South Saskatchewan River, which is fed by three rivers that arise in the mountains, makes its way through dry farmland and prairie. The North and South Saskatchewan rivers join in the province of Saskatchewan and become part of the Nelson-Churchill system, and their waters eventually reach Hudson Bay. There is also the smaller Beaver River, which flows through the heart of the Lakeland Region and then into the Churchill system; and the Milk River, which passes briefly into Alberta from Montana before returning south to flow finally to the Mississippi River and the Gulf of Mexico.

Within these large river basins, water drains into creeks, streams and lakes. The nature of a particular lake depends not only on its physical setting, but also on what enters it from its surroundings. Water enters the lake from its drainage basin, carrying tiny particles of soil and organic matter and dissolved substances, including nutrients such as phosphorus and nitrogen. Water also enters the lake underground. As well, lakes receive dust, precipitation and gases from the atmosphere. Each lake's water quality reflects the contribution of all of these materials, and of sunlight and wind energy.

Within the lake is a complex world of living organisms-the tiny plants called algae that tint the water green, and the large plants that grow in shallow water along the shore. Many animals inhabit or use the lake environment, including fish, waterfowl, muskrats, aquatic insects, snails and tiny crustaceans suspended in the open water. These plants and animals form an interconnected web. Each is dependent on other organisms for food and shelter. They in turn influence the lake's character and its water quality. People, too, may influence the nature of the lake. They control water levels, divert water, change the land in the lake's drainage basin from forest to farm and urbanize the lakeshore.

All of these characteristics are discussed in the following sections. They are provided to assist readers in understanding the detailed descriptions of the 100 lakes included in the Atlas. Table 1 summarizes much of the information provided in each lake description, and allows one to compare various aspects of these lakes. These introductory sections are arranged in the order that they are presented in the individual lake chapters: Drainage Basin Characteristics, Lake Basin Characteristics, Water Quality and Biological Characteristics. These sections are intended to enhance the reader's awareness of a particular lake, or Alberta lakes in general - whether he or she is a cottager, an angler, a student, a scientist or simply a person who appreciates nature, particularly the fascinating world of lakes.

P.A. Mitchell