Identification of aquatic habitats is based, in part, on landscape geomorphology and hydrology. The hydrologic cycle describes the movement of water from the oceans into the atmosphere and across land. In combination with other geological processes, the hydrologic cycle determines many of the physical characteristics of aquatic habitats. This chapter provides some details about the hydrologic cycle and then discusses the physical geology of groundwaters. Chapters 5–7 continue this theme with respect to wetlands, streams, rivers, lakes, and reservoirs. The reader should be aware of the many linkages among different types of aquatic habitats across the landscape, even though we discuss them in separate chapters. An understanding of physiography provides a starting point for examining abiotic factors that drive aquatic ecosystems. While there are not clear lines between what is considered a stream, a wetland, or a lake, scientists have classified freshwater habitats as such based on gradients across axes that based on physical factors. This chapter forms the starting for understanding how these habitats differ.
Freshwater Ecology (Third Edition), Aquatic Ecology, 2020, Pages 73-93,