ENVS 101 1st Edition Lecture 11Outline of Last Lecture I. Water and the Hydrologic CycleII. Water on the GroundIII. Water Under the GroundIV. Water and SocietyOutline of Current Lecture II. Water on the Ground III. Water Under the GroundIV. Water and SocietyCurrent LectureDownstream: width and depth increase gradient decreasesflow velocity and discharge also undergo an increaseLoad particle size decreases Ecosystems undergo changes from place to place, and water temperature is a critical component in the environment because varying temperatures are capable of supporting certainlife forms in ecosystems.with change in water temperatures, scavengers, predators and collectors can vary depending onthe water conditions as well. A common example of a scavenger is a catfish, which roams around the lower parts of the river collecting and distributing river nutrients. At the microscopiclevel, there are scavengers which are known as "collectors" which are the bacteria that can be present within a river.alluvium: sediment that is deposited by a riverBedrock channels often have the rarely sighted straight channels, river banks that resemble a straight line.In the Meandering channels: Straight channels are rareLow gradient dreams typically assume a sinuous shape, each bend is a meander velocity is lowest along inside meanderpoint bar deposition commonly occursVelocity is at its highest along the outside meanders, and because of this, cut bank erosion can occur, because the water effectively cuts away at the outside edges of a meandering channel. By way of this erosion, meanders have a tendency to migrate, and oftentimes, a stream will bypass a channel loop, effectively cutting it off and forming an oxbow lake. They provide These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.standing water, as well as an environment that is different from the original river, influencing theecology of the organisms which live in the river. It also helps organisms which have trouble laying eggs in moving water, so oxbow lakes help amphibians such as frogs, to be able to reproduce in an alternate aqueous environment. Another type of stream pattern is a Braided Channel: A stream with many interlacing channels and bars will be categorized as a braided channelstream that cannot transport the entire sediment load deposit the coarsest and densest sediment as a barBraided channels have a tendency to have variable discharge, as well as easily erodible banks.Straight channels These channels are often in bedrock. or very steep areas, anthropogenicThey also have a tendency to be highly erosiveA local occurrence that demonstrates the changes in our streams:Cochiti Dam captures all of the sedimentRio Grande erodes alluvium downstream to meet its carrying capacity, and the channel as a result becomes more straight, and narrow, as well as deeper. When a channel undergoes these particular changes, it becomes incised.[Week six, part two]Continental Divide: A line which separates the drainage basins that flow into different oceans Continental divides will often coincide with the crests of mountains, the result of uplift, we know that there is a close relationship that occurs between plate tectonics as well as the locations of stream basins.Landforms of Streams:Floodplain: broad deposit of fine sediment beyond the channel made during a floodTerrace: old floodplains abandoned as stream incises and cuts down over timeAlluvial Fan: a fan-shpaed deposit at the base of an upland or mountainous areaDelta: a triangular shaped deposit that is formed when a stream ends up entering standing water, which can pertain to either a sea or a lake. FloodingA natural part to river systems and riparian ecologyCottonwoods require flooded conditions in order to successfully germinateriver discharge exceeds the channel capacity due to :runoff from intense precipitation, and seasonal snowmeltrain on snow events which can be particularly devastating. Most cottonwoods along the Rio Grande are around the same age, but there has been no flooding along the river for just over forty years time. Should this continue, when the cottonwoods start to meet their life expectancy, there won't be any replacements for the trees that will begin to start dying out. Recurrence Interval"Statistical method used to gauge the likelihood of a certain dischargedoes not actually credit the occurrence of a flood, but is instead used to evaluate the risk of such a natural process occurring in a given environment.Flood Prevention:River channels are oftentimes channelized and or dammed for the purpose of flood controlFlood prevention comes at a price, however:- It interferes with the ecosystems which are present along a river environment- It can aggravate the effects of pollution around the area- Flood prevention does not always protect against the effects of flooding, at may actually increase the chances of a flood occurring- It can also lead to subsidence, or sinking. Overall, it can reduce historic hydrologic data as something that is invalid.When dams are built, the evaporation of the water which is stored within these man made reservoirs means less water available for our own use, as well as less water for the organisms that are present in a riparian ecology.Lag time: time between break precipitation and peak