ENVS 101 1st Edition Lecture 10 Outline of Last Lecture I. Plate TectonicsII. Plate motion and the Driving ForceIII. Plate interactions and Earth’s LandscapesOutline of Current Lecture II. Water and the Hydrologic CycleIII. Water on the GroundIV. Water Under the GroundV. Water and SocietyCurrent LectureWhat exactly makes water so important? The distinctive chemical properties of water itself, are what make the very existence of life possible. Among other things, water:- Dissolves and transports elements- Water also dilutes and transports wastes- It is also a key element in supporting biologic structuresWater plays an instrumental role in controlling the surrounding climate on all parts of the Earth, by both moderation of temperature, as well as climate control.Water and the Hydrologic Cycle: The depositional and erosional effects of streams, waves, and glaciers produce a vast and unique diversity of landscapes which are found on our Earth. At a more local level, water in the air, or the humidity percentage that makes up some of the information that we gain from our weather forecasts, can cause huge increase or decrease in the temperature from day to night. On some days, the change that occurs can be as much as thirty degrees, because of the variation in the humidity that is found in the air.The overall movement of water throughout the hydrologic cycle is powered by the Sun, and occurs in the following process:- Evaporation, or Transpiration- Condensation- PrecipitationThese 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.- Surface runoff- Infiltration- Ground waterThe largest reservoir that can be found in the Hydrologic cycle by far, is the ocean. The ocean actually contains the vast majority of Earth’s water, around 97.5% of it!Another interesting aspect of this natural process, is that most of the water in this cycle is saline, making it unusable by humans.The largest reservoir of freshwater on Earth is the polar sheets, which contain approximately 74% of the Earth’s fresh water. The largest reservoir of the unfrozen fresh water that can be found on Earth is groundwater.Water on the Ground: After precipitation occurs, water moves downhill, initially as overland flow, or sheet flow, and then it collects into small channels that are called gullies or rills. After collecting into these small channels, the water then gets concentrated into stream flow.Fire is a natural disaster that has interesting effects on soil, effectively making it more hydrophobic in nature (kind of like a water repellent type of situation). Along with that, fire can decrease the infiltration that occurs in soil with the water cycle, and consequentially, increases runoff that occurs. Fire also kills plants, leaves, and even rootsthat otherwise help to stabilize the soil that they are found in.Steep slopes in a natural environment also increase the likelihood of runoff, as well as soft/erodible soil, or heavy rainfall.There are various types of systems that occur in stream networks, including channels, drainage basins, as well as divides.Discharge: Is the rate of water movement (volume per time), units: cfs (ft3 per second), cumecs (m3 per second)Load: A stream’s total sediment and dissolved matter that it is transportingWater on the Ground:- Bed Load: consists of 5-50% of total sediment load, and moves by rolling, sliding, or saltation.- Suspended Load: Particles of silt and clay effectively provide the muddy characteristics of various streams- Comprised Load: Is comprised primarily of seven different ions (bicarbonate, magnesium, calcium, sulfate, chloride, sodium and potassium)Stream Flow: Consists of the following elements- Storm flow: “extra” water that ends up running off after precipitation- Base flow: water flowing between storms usually supplied by groundwaterStreams that have no base flow are ephemeral, while streams with base flow are perennial.The size and shape of a stream channel are actually controlled by several factors, including: - The erodibility of rock- The steepness of descent - Volume of waterGradient: The vertical distance that a stream channel descends along its course. Overall, this undergoes a decrease as it goes downstream, but this is not a change which occurs very smoothly.Overall, stream behavior is controlled by five distinctive factors, including:1. Average channel width and depth2. Channel gradient, or slope3. Discharge4. Channel pattern 5. Sediment loadAll streams on Earth undergo a different amount of combined effects from the interactions which occur among these distinctive