introduction to hydrology, Lecture notes of Hydrology

Download introduction to hydrology and more Lecture notes Hydrology in PDF only on Docsity! Chapter 1 Introduction Dr. Noraliani Alias Senior Lecturer Hydraulic and Hydrology Department Faculty of Civil Engineering Universiti Teknologi Malaysia 81310 UTM Skudai Johor HYDROLOGY AND WATER RESOURCES Outline of Topics 1.Introduction to Hydrology 2.Rainfall Analysis 3.Hydrologic Losses –Infiltration & Evapotranspiration 4.StreamflowMeasurement 5.Hydrograph Analysis 6.Flow Routing 7.Flow Estimation 8.Frequency Analysis 9. Reservoir & Flow Duration Curve 10. Groundwater Applications of Hydrology • Planning, Design and management works in the Water Resources System • Development of water resources over a river basin • Manage, control and distribute water to urban area, populations, industry, rural area, and agriculture. • Port development, dam construction, hydropower, groundwater (mineral water) well. Water Resource System Can be broadly categorized as: 1.Water Control System 2.Water-Use System Water Control System 1. Drainage 2.Flood Control 3.Salinity Control 4.Sediment Control 5.Pollution Abatement/Reduction Water-Use System 1. Designed to support human habitation. 2. Designed to provide specified levels of service. 3. The design capacity of these systems are generally dictated by the population of the service area, commercial and industrial requirements and the economic design life of the system. The Hydrologic Cycle • The hydrological cycle is the system which describes the distribution and movement of water between the earth and its atmosphere. • The model involves the continual circulation of water between the oceans, the atmosphere, vegetation and land. • Water on the earth exists in a space called hydrosphere. • Water circulates in the hydrosphere through the maze of paths constituting the hydrologic cycle • The hydrologic cycle is the central focus of hydrology • The cycle has no beginning or end, and its many processes occur continuously The Hydrologic Cycle • Much of the intercepted water and surface runoff returns to the atmosphere through evaporation. • The infiltrated water may percolate deeper to recharge groundwater, later emerging in springs or seeping into streams to form surface runoff, and finally flowing out the thesea or evaporating into the atmosphere as the hydrologic cycle continues. The Hydrologic Cycle • Usually the water cylce is in balance, and the amount of precipitation falling will slowly soak into the ground and eventually reach the rivers. • However, if rainfalls for a long period of time or if the ground is already soaked or saturated with water, then the chance of flooding is increased. Water Cycle Balance A Closed System • The hydrologic cycle is a good example of a closed system: the total amount of water is the same, with virtually no water added to or lost from the cycle. • Water just moves from one storage type to another. • Water evaporating from the ocean is balanced by water being returned through precipitation and surface runoff @ UNIVERSITI TEKNOLOGI MALAYSIA Water Balance Lid Precipitation Infiltration Evapotransipration Stream Flow www.utm.my @ UNIVERSITI TEKNOLOGI MALAYSIA Water Balance in Soil Soil Water Balance RAIN IRRIGATION J TRANSPIRATION EVAPORATION “+ ROOT RUNOFF DEPTH ees UPWARD FLOW DEEP PERCOLATION GROUND WATER www.utm.my @ UNIVERSITI TEKNOLOGI MALAYSIA — Evaporation + Transpiration Transpiration Evapotranspiration Transpiration = = Se TT innovative » entrepreneurial « global • The equation uses the principles of conservation of mass in a closed system, whereby any water entering a system (via precipitation) must be transferred into either evaporation, surface runoff (eventually reaching the channel and leaving in the form of river discharge), or stored in the ground. Water Balance Equation • This equation requires the system to be closed, and where it isn’t (for example when surface runoff contributes to a different basin) this must be taken into account. • •A water balance equation can be used to help manage water supply and predict where there may be water shortages Water Balance Equation • The water balance equation also used in irrigation, runoff assessment, flood control and pollution control. • It is used in the design of subsurface drainage systems. • The water balance can be illustrated using a water balance graph which plots levels of precipitation and evaporation often on monthly scale. Water Balance Equation _____—CqWater Balance Equation Py ET Watershed or Catchment Q www.utm.my @ UNIVERSITI TEKNOLOGI MALAYSIA _____—CqWater Balance Equation Water INPUT and OUTPUT is not in balance: Input # output + output P = ET + O P = ET + O + AS P = precipitation/ rainfall ET =evapotranspiration O = streamflow /surface runoff AS = change in water storage www.utm.my @UIM Watershed/ Catchment Water ee! Balance AS (a closed system AG = 0) www.utm.my Example 1: Water Balance Equation A watershed receives average annual rainfall 1000 mm/yr, and a river draining the area with recorded average annual discharge 18 m3/s. Area of the watershed is 103km2. Estimate annual evapotranspiration, ET. Area of watershed = 103km2 Average annual rainfall = 1000 mm/year Average annual streamflow = 18 m3/s S= assume zero ; G= assume zero P = ET + Q + 0 + 0 Q = 18 m3/s = 18 x 60 x 60 x 24 x 365 m3/yr Q = 56.76 x 107m3/yr Area = 103x 1000 x 1000 = 109 m2 Q =[56.76x107/109] = 0.5676 m/yr = 568 mm/yr ET = 1000 mm/year -568 mm/yr ET = 432 mm/year Example 1: Water Balance Equation Example 2: Water Balance Equation A reservoir storage received average annual rainfall 1000 mm/yr, and inflow from a river into the reservoir with recorded average discharge 18 m3/s. Given: the reservoir releases 520 million m3/yr for water used, evaporation 750 mm/year, and percolation 6 million m3/yr. Reservoir surface area is 100 km2. Estimate the annual change in the reservoir storage, S.ΔS. Hydrologic Data Hydrologic data are the building blocks for modeling hydrologic processes. Many sources of data may be accessed to support model development and verification, statistical analysis, and other studies. The quality of data obtained relates to the attributes of measuring instruments and to the features of gauging sites. The capabilities and limitations of measuring devices must be understood Meteorological Data • Humidity and Water Vapour • Solar Radiation • Wind Speed • Temperature • Rainfall • Atmospheric Pressure • Cloud Physic Malaysia Meteorology Service (MMS) •Humidity and Water Vapour •Solar Radiation •Wind Speed •Temperature •Rainfall •Atmospheric Pressure •Cloud Physic Watershed Characteristics/Data •Size, Length, Width, Slope, Pattern •Soil Type & Geology •Land Use & Development •Vegetation Cover •Stream/Channel Network www.utm.my innovative e entrepreneurial e global