Hydrology Study.docx

Hydrology Study What % of all global water is fresh water? 3% What % of fresh water is accessible for direct human use? 0.5% What % of the world’s fresh water is in Canada? What is the dominant human use of water? What % of fresh water is considered “polluted”? Grace - Monitor tiny month-to-month changes in Earth's gravity field that are primarily caused by the movement of water in Earth's land, ocean, ice and atmosphere reservoirs  Identify possible trends in precipitation changes, groundwater depletion and snow and glacier melt rates, and to understand their underlying causes.  Monitors water discharged by freshwater streams from Earth's continents.  GRACE-FO will help monitor droughts Water Characteristics  

Greenhouse gas H2O – covalent bond

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 Hydrogen bonds – very weak but important  Due to slightly negative oxygen and slightly positive hydrogen of a different water molecule  20x weaker than covalent bonds b/w hydrogen and oxygen Expands when heated, contracts when cooled except between 0-4C  Ice less dense than water; floats  Water freezes top-down

Strong inter-molecular forces  Melting and boiling point are higher than for other substances of similar molecular weight • •

Changes in phases of water releases/absorbs more latent heat than most other common substances. Gives water an immense ability to store and transport heat around the globe and affect earth’s energy budget

 In liquid water each molecule is H-bonded on average to 3.4 other water molecules. • Molecules are now allowed into the open spaces of the hexagonal structure. • Allows the molecules to move closer to each other and increases the density. • As T increases towards 4o C, molecules move through the liquid so fast that fewer bonds are formed at any one time, shortening the average time each bond exists and increasing the density even further. • At atmospheric pressure the temperature of greatest density is 4o C Capillary Action: When adhesion to walls is stronger than cohesive forces between liquid molecules  Results in a meniscus Universal solvent:  Heavily attracted to different molecules; forms H-bonds  Surrounds individual ions of substances preventing them from recombining  Implications: transports nutrients through environment, key metabolic changes, carries pollutants Ancient Hydrology: Countless examples  Lost city of Mohenjo-Daro, Pakistan  Nazca Puquois, Peru: Corkscrew design of subterranean aquaducts to direct water flow  Archimedes’ Screw: Water pumped by turning a screw-shaped surface inside a pipe from lowlying bodies of water  Noria Water Wheel  Banaue Rice Terraces, Philippines  Heron’s Fountain John Dalton (1766 – 1844): Proved precipitation = (evaporation + river-flow) Global Water Balance:      

Soil – small total volume but short residence time; turns over several times a year Glaciers/ice – large reservoirs but long residence time Temperate regions: 30% evaporation, 30% runoff, 30% ground water recharge Semi-arid: 50% evaporation, 30% runoff, 20% recharge Arid: 70% evaporation, 30% runoff, ~1% recharge Ocean re-distribute excess runoff  Atlantic Ocean has a deficit in annual precipitation-evaporation balance  Difference compensated by inflows from Arctic and Pacific (have a surplus)

Microscale – soil water Mesoscale – drainage basin Macroscale – global/regional Global Water Issues:  Spatial diversity  Seasonal/long-term variation  Climate variability impacts  Climate change  Population/availability of water resources Vapour Pressure: Pressure exerted by just the water molecules in a given volume of air (in hectopascals, hPa or mbar) Relative humidity (%) = (water vapour content/water vapour capacity)*100    

Can change by changing water vapour content Or changing air temperature For each 1C rise, 6% increase in amount of water vapour air can hold Dew point: temperature at which water vapour begins to condense out of air  Closer the air temp and dew point = higher relative humidity  When air temp = dew point, RH = 100%

Adiabatic Lapse Rate (ALR): Rate at which temperature of an air parcel changes vertically through the troposophere  Dry ALR: Lapse rate of 10C/1000m  Moist ALR: 6C/1000m  Air parcel expands and cools as it is lifted Over a mountain      

Warm air rises, less dense As it rises, air pressure decreases around it To equalize pressure difference, parcel expands Air molecules use energy to expand Loss of energy = parcel cools

Air will always expand and cool as it rises, and compress and warm as it sinks

Latent Heat

Stable: Saturated or Moist ALR; Saturday air parcel is warmer than surrounding air Unstable: Air continues to rise, eventually reaches condensation  Parcel stops when surrounding temperature is the same  Higher clouds = more intense rainfall Rainfall is most abundant where air rises and cools Rainfall is least abundant where air sinks Greatest rainfalls at ITCZ and monsoon climates

Kriging: Statistical method that uses the variogram (variance between pairs of points at different distances) to assign weightings for different gauges to minimize estimation error  Can be used to generate a map, quantify statistical structure of rainfall patterns  To design a more effective network Satellites and Rainfall:  Albedo: high brightness = thicker cloud = higher probability of rainfall  Infrared imagery: Low T + high cloud tops + large thickness = higher probability of rainfall  Rain more likely in cold and bright clouds Precipitation Parameters: Amount (L), Duration (T), Intensity (L/T)

Water Balance Equation Inflow = Outflow ± Δ Storage

Interception: Water abstracted from gross precipitation by leaves and stems of a vegetation canopy and temporarily stored in its surfaces  By tree canopys, grass, built structures  Net Rainfall: Precipitation that reaches the ground  Interception can be quite large which effects water balance Interception Loss: Intercepted water lost to the atmosphere by evaporation before reaching the soil surface  Amount left on leaves after rain stops  More dependent on short-term variations in rainfall (storms)  Additional effects:  Higher at nighttime  Interception storage capacity of vegetation  Age/species of trees (larger canopy) 3 Different Effects from Interception 1: Mechanical Effects from Interception – reduction of force from raindrops hitting soil  Reduces erosion and soil loss  Unprotected soil subject to 3 erosional effects: 1. Fine material may be washed into larger pores 2. Solid particples moved by impact of raindrops 3. Exposure of soil to greater temperature ranges and desiccation causes soil aggregates to break down 2: Quantitative Effects from Interception – reduction in precipitation that reaches soil  Precipitation intercepted by forest evaporates at a greater rate than transpiration from the same type of vegetation in the same environment (2-5x)  Losses decrease when interception storage is filled 3: Conservational Effect – several aspects of interception process favour conditions where soil moisture may be maintained Aerodynamic resistance: resistance encountered by water vapour moving from the vegetation surface as wet surface evaporation into the surrounding atmosphere

Controls on Amount of Interception Vegetation form/structure: Shape, broad vs. needle, Number of leaves/stems, Branch/leaf orientation Vegetation growth pattern/physiology:

Seasonal growth, age, growth rate, Leaf Area Index (LAI) Meteorological Conditions: Precipitation intensity/duration, Snow/rain/sleet etc., Wind speed/turbulence