01-Introduction-to-Hydrometeorology.pdf

Central Luzon State University COLLEGE OF ENGINEERING DEPARTMENT OF AGRICULTURAL AND BIOSYSTEMS ENGINEERING ABEN 3410 - Hydrometeorology INTRODUCTION Carolyn Grace G. Somera Professor Hydrology Is ‘the science or study of’ (‘logy...

Central Luzon State University COLLEGE OF ENGINEERING DEPARTMENT OF AGRICULTURAL AND BIOSYSTEMS ENGINEERING ABEN 3410 - Hydrometeorology INTRODUCTION Carolyn Grace G. Somera Professor Hydrology Is ‘the science or study of’ (‘logy’ from Latin logia) ‘water’ (‘hydro’ from Greek hudor). It is the science dealing with the occurrence, circulation, distribution, properties and reactions with the environment of waters of the Earth. http://www.cesm.ucar.edu/models/clm/images/hydrology.jpg Branches of Hydrology Chemical Study of chemical characteristics of water Hydrology Chemistry of water in rivers and lakes, both of Water Quality pollutants and natural solutes Study of interactions of living organisms and the Eco Hydrology hydrologic cycle Study of the distribution and movement of Hydrogeology groundwater in the soils and rocks of the Earth’s crust Branches of Hydrology Study of the transfer of water and energy Hydrometeorology between land and water body surfaces and the lower atmosphere Surface Study of hydrologic processes that operate at or Hydrology near Earth's surface Drainage Basin Covers water-storage, in the form of reservoirs, Management and flood-protection Meteorology Comes from the Greek word Atmospheric water in the form of clouds ‘meteõros’ meaning ‘high in the air’. It is the science of atmospheric phenomena and processes, especially weather and weather conditions.  It is the Wind instantaneous or Weather current state of PrEcipitation the Earth’s atmosphere Atmospheric Pressure Temperature Humidity It is long-period manifestation of Cloud & StatE of the Sky Climate weather. HoRizontal Visibility Weather Elements Weather and Climate Differences WEATHER CLIMATE Weather is the study of atmospheric Climate is the study of the conditions for short duration of a average weather conditions limited area. observed over a long period of time for a larger area. Weather is influenced by anyone of its Climate is the collective predominant elements. effect of all its elements. The weather changes very often. It is more or less permanent. It is experienced over small areas of a It is experienced over large area of country. the continent. A place can experience different types of A place can experience only weather conditions in a year. one type of climate. Hydrologic Cycle continuous movement of water above, on, and below the surface of the Earth continuous exchange of water between atmosphere, land, surface and subsurface waters, and organisms https://www.ec.gc.ca/eau-water/23CEC266-78F4-4316-93FC- D795EF692D62/Hydrologic.gif Hydrologic Cycle Used to model the storage and movement of water between the biosphere, atmosphere, lithosphere and hydrosphere. https://briangrimmerblog.files.wordpress.com/2014/07/image.jpg http://eschooltoday.com/earth-system/images/what-is-in-the-biosphere.png Water reservoir Lakes Oceans Groundwater Glaciers Rivers Snowfields Soils Water movement Evaporation Liquid to gas Condensation Gas to liquid Precipitation Water that falls to the ground Deposition Gas to solid Portion of water that flows over the Runoff ground surface Water movement Infiltration Water that infiltrates through the soil Sublimation Solid to gas Give off water vapor through plant Transpiration pores Groundwater Part of streamflow that has infiltrated flow the ground Hydrologic Cycle Human Activities Affecting the Hydrologic Cycle and Watershed Deforestation https://s-media-cache- ak0.pinimg.com/originals/ee/2b/ef/ee2befae8d6376d7 http://ac4.ei.columbia.edu/files/2014/04/img2.jpg a33720c71b6e7ed1.jpg Cutting down trees increases run-off, decreases evapotranspiration (and therefore cloud formation) and leads to more extreme river flows. Human Activities Affecting the Hydrologic Cycle and Watershed Irrigation http://negroschronicle.net/web-archives/photos/july_07_13/infertile- http://www.ecagdev.agecon.vt.edu/Chapter%205/Picture22.jpg irrigation.jpg Taking water from a river or underground store can reduce river flow, lower water tables and increase evaporation/evapotranspiration. Human Activities Affecting the Hydrologic Cycle and Watershed Urbanization The removal of natural vegetation and replacement with impermeable surfaces and drains can speed up overland flow and evaporation and can lead to higher river levels. It also decreases the amount of water which returns to groundwater storage. Human Activities Affecting the Hydrologic Cycle and Watershed Mining Lead to reduced vegetation cover leading to increased run-off, higher evapotranspiration and cloud formation altering the rainfall pattern. Breaking up of rocks leads to http://2.bp.blogspot.com/-W- increased silting up of lakes, _BwFVfm_o/UJ0K7Es2EjI/AAAAAAAAtRU/8DTmp8wafis/s1600/Illegal%2BMini ng%2BPhilippines-728119.jpg rivers and reservoirs leading to reduced storage capacity in these areas. Human Activities Affecting the Hydrologic Cycle and Watershed Dam Building Greatly reduces the discharge of a river as storage is increased. Leads to increased evaporation and therefore can alter rainfall patterns. http://blog.conservation.org/wp- content/uploads/2016/01/ci_42759890_Small.jpg  Earth’s Water Distribution https://www.sciencelearn.org.nz/system/images/images/000/000/802/full/H2O_SCI_ART_04_ waterorigins_waterdistribution.jpg?1492686296 The Hydrologic Budget An equation showing 𝑷 − 𝑹 − 𝑮 − 𝑬 − 𝑻 = ∆𝑺 all of the inputs into the system minus the P = Precipitation outputs of the system, R = Runoff resulting in the G = Groundwater flow change of the amount E = Evaporation of water in the system under consideration. T = Transpiration ∆𝑺 = Change in storage The Hydrologic Budget Precipitation Evapotranspiration Surface water Surface water Groundwater Groundwater inflows outflows (Infiltration) (Exfiltration) Change in water storage = change in water level (inches or depth) If input > output, +∆S If input < output, -∆S The Hydrologic Budget Graphical representation of water budget Hydrologic Budget Equation We can expand the water budget equation into [in consistent units], ±∆𝑆 = 𝑃 + 𝑅𝑖𝑛 − 𝑅𝑜𝑢𝑡 + 𝐺𝑖𝑛 − 𝐺𝑜𝑢𝑡 − 𝐸𝑇 ±∆𝑆 = 𝑃 + ∆𝑅 + ∆𝐺 − 𝐸𝑇 where: ∆𝑆 – Change in storage; 𝑃 – Precipitation; 𝑅𝑖𝑛 – Runoff inflow; 𝑅𝑜𝑢𝑡 – Runoff outflow; 𝐺𝑖𝑛 – Groundwater inflow; 𝐺𝑜𝑢𝑡 – Groundwater outflow; 𝐸𝑇 – Evapotranspiration Sample Problem No. 1 A lake had a water surface elevation of 103.2 m above datum at the beginning of the month. At the same month, lake received an average inflow of 6 cms (m3/s) from surface runoff sources. For the same period, the outflow from the lake had an average value of 6.5 cms. Further, in the same month the lake received a rainfall of 145 mm and losses due to evaporation of 6.1 cm. Assume the area of the lake is 5000 ha and assume no contribution from ground water storage. What is the water surface elevation of the lake after the month? Given: Area = 5,000 ha Time/Duration = 1 month = 30 days Initial water surface elevation = 103.2m Runoff Inflow = 6 cms Inflows: rainfall and runoff inflow Runoff outflow = 6.5 cms Rainfall = 145 mm Evaporation = 6.1 cm Outflows: evaporation and runoff outflow Assume no ground water flow Calculate the new water level, that is, 𝑁𝑒𝑤 𝐿𝑒𝑣𝑒𝑙 = 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑙𝑒𝑣𝑒𝑙 ± ∆𝑆 Solve the change in storage using the equation: ±∆𝑆 = 𝑃 + 𝑅𝑖𝑛 − 𝑅𝑜𝑢𝑡 + 𝐺𝑖𝑛 − 𝐺𝑜𝑢𝑡 − 𝐸𝑇 ±∆𝑆 = 𝑃 + ∆𝑅 + ∆𝐺 − 𝐸𝑇 Eliminate groundwater flow since it is assume to be zero. ±∆𝑆 = 𝑃 + 𝑅𝑖𝑛 − 𝑅𝑜𝑢𝑡 − 𝐸𝑇 ±∆𝑆 = 𝑃 + 𝑅𝑖𝑛 − 𝑅𝑜𝑢𝑡 − 𝐸𝑇 Before using the equation, remember to make their units consistent. We commonly expressed them in terms of depth. 𝑚3 3600𝑠𝑒𝑐 24ℎ𝑟 𝑅𝑖𝑛 =6 × × × 30𝑑𝑎𝑦 = 15,552,000𝑚3 𝑠𝑒𝑐 1ℎ𝑟 1𝑑𝑎𝑦 𝑚3 3600𝑠𝑒𝑐 24ℎ𝑟 𝑅𝑜𝑢𝑡 = 6.5 × × × 30𝑑𝑎𝑦 = 16,848,000𝑚3 𝑠𝑒𝑐 1ℎ𝑟 1𝑑𝑎𝑦  1 𝑅𝑖𝑛 = 15,552,000𝑚3 × 2 = 0.31104𝑚 = 𝟑𝟏𝟏. 𝟎𝟒𝒎𝒎 5000ℎ𝑎 × 10000𝑚 Τℎ𝑎 1 𝑅𝑜𝑢𝑡 = 16,848,000𝑚3 × 2 = 0.33696𝑚 = 𝟑𝟑𝟔. 𝟗𝟔𝒎𝒎 5000ℎ𝑎 × 10000𝑚 Τℎ𝑎 𝑃 = 𝟏𝟒𝟓𝒎𝒎 𝐸𝑇 = 6.1𝑐𝑚 = 𝟔𝟏𝒎𝒎  The change in storage is 58.08mm, which means the lake gains water (since it is positive). ±∆𝑆 = 𝑃 + 𝑅𝑖𝑛 − 𝑅𝑜𝑢𝑡 − 𝐸𝑇 By multiplying 58.08mm increase to the area Substitute the calculated values: of the lake will give you the volume of water increased. 𝑅𝑖𝑛 = 311.04𝑚𝑚 𝑅𝑜𝑢𝑡 = 336.96𝑚𝑚 New water level = initial water level + ∆𝑆 𝑃 = 145𝑚𝑚 𝐸𝑇 = 61𝑚𝑚 New water level = 103.2m + 0.05808m = 103.258 m above the datum ±∆𝑆 = 145 + 311.04 − 336.96 − 61 ±∆𝑆 = 58.08𝑚𝑚 Sample Problem No. 2 A lake has an area of 10 km2. During a specific month the lake evaporation was 90 mm. During the same month the inflow to the lake from a river was on average 1.1 m3/s and the outflow from the lake via another river was on average 1.2 m3/s. Also, for the same month a water level increase of 100 mm for the lake was observed. What is the precipitation during the month? Assume: no groundwater flow. Quiz No. 1 A small catchment basin with area of 150 ha received a rainfall of 10.5 cm in 90 minutes due to storm. At the outlet of the catchment, the stream draining the basin was dry before the storm and later experience a runoff lasting for 10 hrs with an average discharge of 1.5 cms when rainfall occurs. The stream was then again dry after the runoff event. a) determine the amount of water which was not available to runoff due to combined effect of infiltration, evaporation and transpiration, b) what is the ratio of runoff to precipitation? References Subramanya, K. (2008). Engineering Hydrology, 3rd Ed., pp 1-3. New Delhi: Tata McGraw-Hill Publishing Company Limited. Bruce, J., R. Clark. (1966). Introduction to Hydrometeorology, pp 1-2. Oxford: Pergamon Press Ltd. https://www.open.edu/openlearn/science-maths- technology/science/environmental-science/water-use-and-the-water- cycle/content-section-2.1