Hidrology Note Topic 1

Definition

Hydrology is the science that takes into account the water in the world, existence, and the distribution cycle, chemical and physical properties, and reactions to the environment, including relationships with living things. Space covers the entire history of existence of water on the earth

Hydrology

Hydro – Water (air)Logy – Research about (kajian tentang)

Measuring Unit of Watera) Depth (mm, cm, m, inch, feet)b) Volume (cm3, m3, liter, cube feet, meter hecta(m-ha)c) Flow rate (liter/sec/minutes/hours, m3/s)

HIDROLOGY DATA CRITERIA

• Trusted• Continuously

Data can be obtained from Jabatan Kaji Cuaca Jabatan Kerja Raya Jabatan Bekalan Air Jabatan Geologi dan ukur Jabatan Alam Sekitar

Hydrological Cycle

• A transition cycle of water (water transfer) that occur on earth consistently and naturally

Hydrological Cycle Precipitation (P) - Curahan Evapotranspiration (E) – Sejat Peluhan Evaporation - Sejatan Transpiration (T) - Pepeluhan Surface Run-Off (R) – Larian Permukaan Infiltration (I) – Penyusupan Ground Water (G) – Air Bumi Condensation (C) – Pemeluwapan Convection - Olakan

Basic Components of the hydrological Cycle

Precipitation The transfer from vapor form to liquid form. It is a

continuous process in which water is evaporated from oceans, moves inland as moist air masses.

The precipitation that falls from clouds onto the land surface. For example - rain , snow, dew, hills

Evaporation /Evapotranspiration The transfer of water from liquid form to vapor form. Rainfall is retained in the soil near where it falls and returns to the atmosphere

Transpiration (T) Water inside of plants is transferred from the plant to the atmosphere as water vaporInfiltration (I) Infiltration is the physical process involving movement of

water through the boundary area where the atmosphere interfaces with the soil. Part of rain water infiltrated to the soil due to gravitational force and pressure different.Surface Runoff (R) The transfer of liquid form within a catchment areas surface runoff that flows over the land surface and through channels, subsurface runoff that infiltrates the surface soils and moves laterally towards the stream

Effect of land use to the hydrological cycle

• Land slide• Land erosion• Flood• Global Warming• Land Pollution• Water Pollution• Air Pollution

Hydrolologic Continuity Equation(The water Balance)

A statement about water balance and water conservation law accurring in a clearly defined catchment area.dS/dt = I – OdS/dt = rate of storage changeI = amount of water inputO = amount of water output

Example of Calculation• A storage allow to received inflow and outflow

respectively at rate 10 and 15 m3/s for 24 hours. Calculate the change of volume in that storage in 24 hours.

• dS/dt = I – O• dS = (I – O) dt• dS = (10-15) m3/s x[ 24 x 60 x 60]s• dS = - 4.32 x 105 m3

• In two month Padang Melati district predict to received rain 240 mm. Evaporation is 80 mm and infiltration 20 mm. The catchment are is 56 km2 .

• Estimate the volume of surface runoff.• R = P – E – T – I • P = 240 mm• E = 80 mm• T = 0• I = 20 mm

• R = P – E – T – I• = 240 – 80 -20 • = 140 mm @ 0.14 m• Volume of surface runoff• = R x Area• = (0.14) x ( 56 x 106)• = 7.84 x 106 m3

Problem Set1. Explain the hydrological process below

– Infiltration– Transpiration– Base Flow

2. There are two rivers flow into the catchment area 1500 km2. The total discharge of two rivers are 7.5 x 1010 m3/year. Record are made showing the loss due to the transpiration is 10% of the monthly rainfall. Determine the average monthly rainfall for the catchment area.

Problem Set

3. Sungai Kinta catchment is expected to receive 240mm of rain. Transpiration is approximately 55 mm and the infiltration is estimated 20 mm. The catchment area is 65 km2. Estimate the volume of runoff.4. The stream’s storage reach at a particular time is 72 x 103 m3. At that time the inflow and outflow of the stream are 16m3/s and 25 m3/s respectively. Two hours later the inflow and outflow are 23 m3/s and 30 m3/s respectively. Calculate the change and the new storage of the reach at the end of two hours.

5. The drainage area of a village is 2.59 x 1010 m2. If the mean annual runoff is determined to be 19.82 m3/s and the average annual rainfall is 20 cm, estimated the evapo transpiration losses for the area in cm/year.6. State four characteristics of rainfall and the measurement unit.7. Within 6 months of the Sungai Lui catchment area is estimated to receive rainfall of 350 mm. Evaporated in the estimate of 100 mm and diffusion into the subsurface is estimated to 40 mm. Estimate the volume in cubic meters of area to be stored in the reservoir if the basin area is 85 km2.8. Calculate the average daily evaporation rate in (ha.cm)/day on annual evaporation from lake with a surface area of 25 x 106 m2 is 320 cm. (1ha = 10000 m2)

Unit Converter Exercise65 km2 – m2

72000 m3/year – cm3/day8.5 x 103 m3/year – cm3/month157 cm – m82 mm – m482 mm3 – m3

300 ml – cm3

57 cm3 – m3

360 mm2 – m2 250 cm3/month - m3/s