BESC 201, Introduction to Bioenvironmental Science



BESC 320 – Water and Bioenvironmental Science(Lecture 3 – 17 January 2020)Reminder—find water stories in the news for discussion on FridayMore on hydrogen bonding.Hydrogen bonds are relatively weak (e.g. compared to ionic bonds), but water is so hydrogen rich that the summative effect and architecture of the molecule allow the hydrogen bonds to create extraordinary extra-molecular phenomena.The clumping of hydrogens on one side of water molecules pull on the hydrogen-poor sides of adjacent molecules, making weak but numerous (hydrogen) bonds.As with most elements and many molecules, water can exist as solid, liquid, and gas. It is the an extremely exceptional molecule for existing in all three states at temperatures typical to the narrow range of habitable conditions of our planet.The low density in crystalline solid form is due to special geometry of these polar molecules with hydrogen bonding. The architecture of water crystals looks like:In the top row, see the 38 ° alternation of molecules.In this second row, the bottoms of the hexagonal structure, a hydrogen is held out toward us. These bond the next sheet which looks just like this one:Reflect – So why are snowflakes not all alike?Reflect – Why are the atoms not more tightly packed?It is also extremely exceptional for being less dense as a solid than as a liquid.The density of water by temperature looks like:The red arrow indicates maximum density at 4 °C.Reflect – How might this create the strange phenomenon where water bodies freeze beginning at the surface?(demo, images) Reflect – What if Earth were Titan? (approved Wiki, see esp. ?3)Visualize this...Seas of liquid methaneSkies filled with methane cloudsMethane rain (brief NASA report)Frozen methane in ground, on ground, in the seaMethane cryovolcanoes (I kid you not!) Here is methane’s temperature-density curve:It freezes at -182 °C and boils at 161 °CWhere does the methane ice form?Visualize this...Pour yourself a cocktail of liquid methane and waterCool it. Apply immense pressure.Sidebar – There is copious methane ice on Earth (link1) and this may in coming centuries have immense consequences for climate (link2).Be careful, methane ice burns (vid) Last bit on methane—it has interesting interactions with waterIt is produced on Earth by organic decay and may be trapped below ground or liberated from soil to the atmosphere.When produced in the organic-rich sediments of lakes it can become trapped in water ice as it bubbles up from the benthos.This accounts for the strange but real phenomenon of flammable lakes.Methane hydrates are formed by microorganisms that live in the deep sediment layers in the oceans. These are both a potential energy source, surpassing methane gas reserves, but also a serious and synergistic climate hazard. Water is also extremely exceptional for its high latent heat (heat required to cause phase change)For water these plateaus are very longThus water also has high thermal inertiaReflect – Why might this be important at varied scales cellular to global?Water physical sciences II (geology)The global water pool:Water, liquid and solid, covers more than 70% of world’s surfaceMore than 370 billion billion gallons97 % is salt water, mostly in the oceans2.5 % (Water Atlas, Boberg 2005) is freshOf the freshwater...most is ice (70 %)a minority is groundwater (29 %)a small portion (1 %) is surface waterGroundwater can be shallow replenishable sources or deep, slowly- or non-repleneshing fossil water.Shallow water is accessible but requires energy and technologyThus, for most of the human population, available water is well under 1% of the total, like asking for a cup of water and getting 29 Drops in Your Cup ?.Table of volumes & residence times (for concepts only)Residence time relates to sustainability of usePrecipitation largely determines turnover (inverse of residence time)Here is the average global continental precipitationHere is a relatively recent local perspective:In 2011, TX averaged 14.9" rainfallNormal rainfall in TX is 34.25"the value is generally about For perspective, Harvey dropped over 60" in places (30" on my property)Hydrologic CycleBe able to describe key components:Evaporates or transpires from land, water, organisms Condensation (dew or cloud formation)Precipitation (rain, snow)Storage (water bodies, floodplains, groundwater, glaciers)Infiltration (movement of water into soil)Percolation (movement of water through soil to zone of saturation)Runoff (surface movement of water into rivers and water bodies)Water table (after precipitation, the river pushes water into the landscape; otherwise, the landscape pushes water into and sustains the river)Blue water is ?freshwater ?surface and ?groundwater. It is stored ?in lakes, ?streams, ?groundwater, ?glaciers and ?snow.Green water is terrestrial freshwater in biological flux, in soil and soil-life such as plants where flux is by evapo-transpiration and infiltration.?(Practice thinking through these types of water and sustainability for agricultural use. A beginning discussion is in Boberg 2005)Solar energy drives the hydrologic cycle (be able to describe how) Your notes: Solar energy ultimately drives nearly everything in planetary physiology, with water as the planet’s life’s blood.Continental dynamics of water is contained in watersheds in which water moves by gravity obstructed by topology and surface and subsurface composition.The nexus of river forks point the direction of flow (e.g. also indicates declination on landscape gradient). See example topography at right.Things happening in one part of the watershed influence everything downstream and much below ground.Changes in water volume, flow and composition along the gradient also creates ecological diversity.Stream order—literally, the order in which streams occur from high to low gradient. Headwaters are 1st order, and the larger rivers that go to sea are typically 4th order or higher. Practice this on the map above or on Google Earth.Low order streams—small size, rapid gradient change, fast flow, clear & clean (oligotrophic) water, carries few but large parent materials. High order streams—opposite the descriptors given for low order.Oligotrophic—sparse feedingby few but diverse types of organismsfeeding off a limited production base due to low nutrients in the waterEutrophic—true feasting by many but few types of organismsfeeding off a large production base due to high nutrients in the waterMesotrophic—intermediate state in the gradients defined aboveStream geomorphology Gradients, pathways, and architecture of flowing water. Cross section of a riverRiver morphologySinuous paths are typical, especially for low-order streams.This morphology holds a lot of water. Imagine a straight channel of water, 1 m deep, 10 m wide, going straight to Houston. Think about what volume of water that channel holds. Now imagine a highly sinuous path with the same depth and width. How does that volume of water compare?A major useful characteristic (function) of natural, reticulate, sinusoidal riverways is storage of water. When storage capacity is exceeded, floodplains generally contain the remainder.Floodplains are natural parts of evolved stream structureA floodplain is the natural basin in a watershed that floods during times of seasonally high precipitation. Floodplain flora are highly adapted to the flood regimePresence of floodplain prevents flooding elsewherePhotos—Floodplain (above). A river based city absent floodplains (below)Here is a typical (normal) hydrographWhat hydrograph information would be important for:urban planners?natural resource managers?others?Channelization (local flood control that “passes the buck”)Straightening stream paths, often accompanied by concrete walls and runs Guides water quickly downstream, away from the control zoneThis water becomes the problem of those downstreamDevelopment in floodplain or other areas of watershed has the same effect as channelization. Prevention of infiltration and percolation by impermeable surfaces like asphalt direct water quickly over the surface to rivers and low lying areas. Local example: Bryan Target [realtime link]“They paved paradise, put up a parking lot. Put the trees in a museum, charged a dollar and a half just to see ‘em” —Jonie MitchellSo urbanization hastens surface flow.Fast flow creates erosionin channelsbut also on banksespecially outer banksThe outer part of a turn is where momentum sends the bulk of water, and outer parts of a turn, for the same riverwise net flow, require greater velocity, much like the outer tire of your car must turn faster than the inner tire to round curvesYin. This process cuts outer banks of river bends into ever larger loops, so much so that the stream path becomes increasingly meandering. Meanders of high order rivers are a hallmark of unhampered geomorphological evolution. Meanders often intersect in time, at which point loops may get cut off from the main river channel to form an oxbow lake. Yang. As the outer bank is cut and erosion carries away sediment in the fast outer-loop water, the inner parts of curves slow (or sometime reverse!). Slow water cannot carry sediment and the inner curve becomes a net area of deposition. You can see the alluvium on these aerial views. P hotos—Erosion/alluvium ?, meandering and oxbows.Nice animation: meander and oxbow hydromorph (YouTube) We discussed the importance of rivers for holding water. That trait is an example of an ecosystem service. Try to apply the concept throughout the course.Discussion:What are some other ecosystem services provided by rivers? What are some of the consequences of using these services?Required reading: FoodWater supplyTransportationNutrient cycling/tranportHydropower / NRGWilflife & fisheries habitatFlood controlIrrigationRecreationAestheticWashing“Your education really is the job of a lifetime and it commences now.” David Foster Wallace ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download