General Outcomes :Explain the hydrological cycle

Specific Outcomes : ◦ Define the following aspects of hydrological cycle:◦ Explain the relationship between precipitation,

run-off, infiltration and evaporation

TOPIC 1 : UNIT 1

Water is the source of all life on earth. The distribution of water, however, is quite

varied; many locations have plenty of it while others have very little.

Water exists on earth as a solid (ice), liquid or gas (water vapor).

Oceans, rivers, clouds, and rain, all of which contain water, are in a frequent state of change (surface water evaporates, cloud water precipitates, rainfall infiltrates the ground, etc.).

However, the total amount of the earth's water does not change.

The circulation and conservation of earth's water is called the "hydrologic cycle".

The hydrologic cycle is a conceptual model that describes the storage and movement of water between the biosphere, atmosphere, lithosphere, and the hydrosphere

Water on this planet can be stored in any one of the following reservoirs: atmosphere, oceans, lakes, rivers, soils, glaciers, snowfields, and groundwater.

Water is continually cycled between its various reservoirs. This cycling occurs through the processes of evaporation, condensation, precipitation, deposition, runoff, infiltration, sublimation, transpiration, melting, and groundwater flow.

The Hydrologic Cycle

The Hydrologic Cycle process :

Evaporation The transformation of water from a liquid into a gas, a process which humidifies the atmosphere.

Condensation The transformation of water from a gas into a liquid, and the processes that lead to condensation.

Transport The movement of water through the atmosphere.

Precipitation The transfer of water from the atmosphere to land. Rain, snow, hail, sleet, and freezing rain are discussed.

Groundwater Water located below ground and how it returns to the surface.

Transpiration Transfer of water to the atmosphere by plants and vegetation.

Runoff Rivers, lakes, and streams transport water from land to the oceans. Too much rainfall can cause excess runoff, or flooding.

the conversion of water from a gas into a liquid

Condensation is the change of water from its gaseous form (water vapor) into liquid water. Condensation generally occurs in the atmosphere when warm air rises, cools and looses its capacity to hold water vapor.

transport of water vapor around the globe

In the hydrologic cycle, transport is the movement of water through the atmosphere, specifically from over the oceans to over land.

Most water is transported in the form of water vapor, which is actually the third most abundant gas in the atmosphere. Water vapor may be invisible to us, but not to satellites, which are capable of collecting data about the moisture content of the atmosphere.

transfer of water from the atmosphere back to earth.

Precipitation is the primary mechanism for transporting water from the atmosphere to the surface of the earth.

There are several forms of precipitation, the most common of which for Malaysia is rain. Other forms of precipitation include; hail, snow, sleet, and freezing rain.

Rain occurs when clouds containing water will go down in rain form where it functions to supply water to the trees.

Rainfall distribution and intensity will affect:a. water in the soil,b. rate of water loss from the root zone andc. the rate of erosion on the soil surface.

There are three terms used to describe the characteristics of rainfall intensity, total rainfall and frequency.

Rain intensity - rainfall rates within a certain period of time.

.The unit used is mm / hr. Changing the intensity of rainfall during the rainy period

The relationship between rainfall intensity and time, the rainfall is ideal as depicted in graph below:

Keamatan Maksimum

Keamatan

Masa

Hampir linear

Total rainfall-Total rainfall is Accumulated rainfall at one place, whether for a single rain or for a certain period. (monthly, anually total rainfall)

Mm unit Rainfall frequency -The frequency of rain is

min. of rain for certain period in which rainfall intensity and amount determined expected to be occured.

Groundwater is all the water that has penetrated the earth's surface and is found in one of two soil layers.

The one nearest the surface is the "zone of aeration", where gaps between soil are filled with both air and water.

Below this layer is the "zone of saturation", where the gaps are filled with water.

The water table is the boundary between these two layers. As the amount of groundwater water increases or decreases, the water table rises or falls accordingly.

When the entire area below the ground is saturated, flooding occurs because all subsequent precipitation is forced to remain on the surface.

Water is transferred from the surface to the atmosphere through evaporation, the process by which water changes from a liquid to a gas.

Approximately 80% of all evaporation is from the oceans, with the remaining 20% coming from inland water and vegetation. Winds transport the evaporated water around the globe, influencing the humidity of the air throughout the world.

transfer of water from plants to the atmosphere

Transpiration is the evaporation of water into the atmosphere from the leaves and stems of plants.

Plants absorb soilwater through their roots and this water can originate from deep in the soil. (For example, corn plants have roots that are 2.5 meters deep, while some desert plants have roots that extend 20 meters into the ground). Plants pump the water up from the soil to deliver nutrients to their leaves.

Transpiration accounts for approximately 10% of all evaporating water.

Just as you release water vapor when you breath, plants do, too – although the term "transpire" is more appropriate than "breath." This picture shows water vapor transpired from plant leaves after a plastic bag has been tied around the stem for about an hour. If the bag had been wrapped around the soil below it, too, then even more water vapor would have been released, as water also evaporates from the soil.

Plants put down roots into the soil to draw water and nutrients up into the stems and leaves. Some of this water is returned to the air by transpiration.

Transpiration rates vary widely depending on weather conditions, such as temperature, humidity, sunlight availability and intensity, precipitation, soil type and saturation, wind, and land slope.

During dry periods, transpiration can contribute to the loss of moisture in the upper soil zone, which can have an effect on vegetation and food-crop fields.

Plant transpiration is pretty much an invisible proces – since the water is evaporating from the leaf surfaces, you don't just go out and see the leaves "breathing". Just because you can't see the water doesn't mean it is not being put into the air, though.

One way to visualize transpiration is to put a plastic bag around some plant leaves. As this picture shows, transpired water will condense on the inside of the bag.

The amount of water that plants transpire varies greatly

geographically and over time. There are a number of

factors that determine transpiration rates: Temperature:Transpiration rates go up as the

temperature goes up, especially during the growing season, when the air is warmer due to stronger sunlight and warmer air masses. Higher temperatures cause the plant cells which control the openings (stoma) where water is released to the atmosphere to open, whereas colder temperatures cause the openings to close.

Relative humidity: As the relative humidity of the air surrounding the plant rises the transpiration rate falls. It is easier for water to evaporate into dryer air than into more saturated air.

Wind and air movement: Increased movement of the air around a plant will result in a higher transpiration rate. This is somewhat related to the relative humidity of the air, in that as water transpires from a leaf, the water saturates the air surrounding the leaf. If there is no wind, the air around the leaf may not move very much, raising the humidity of the air around the leaf. Wind will move the air around, with the result that the more saturated air close to the leaf is replaced by drier air.

Soil-moisture availability: When moisture is lacking, plants can begin to senesce (premature ageing, which can result in leaf loss) and transpire less water.

Type of plant: Plants transpire water at different rates. Some plants which grow in arid regions, such as cacti and succulents, conserve precious water by transpiring less water than other plants.

Evapotranspiration (ET) is a term used to describe the sum of evaporation and plant transpiration from the earth's land surface to atmosphere.

Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies.

Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata in its leaves.

Evapotranspiration is an important part of the water cycle. An element (such as a tree) that contributes to evapotranspiration can be called an evapotranspirator.[1]

Potential evapotranspiration (PET) is a representation of the environmental demand for evapotranspiration and represents the evapotranspiration rate of a short green crop, completely shading the ground, of uniform height and with adequate water status in the soil profile. It is a reflection of the energy available to evaporate water, and of the wind available to transport the water vapour from the ground up into the lower atmosphere. Evapotranspiration is said to equal potential evapotranspiration when there is ample water.

Anywhere in the world, a portion of the water that falls as rain and snow infiltrates into the subsurface soil and rock. How much infiltrates depends greatly on a number of factors.

Some water that infiltrates will remain in the shallow soil layer, where it will gradually move vertically and horizontally through the soil and subsurface material. Eventually, it might enter a stream by seepage into the stream bank.

Some of the water may infiltrate deeper, recharging ground-water aquifers. If the aquifers are porous enough to allow water to move freely through it, people can drill wells into the aquifer and use the water for their purposes.

Water may travel long distances or remain in ground-water storage for long periods before returning to the surface or seeping into other water bodies, such as streams and the oceans.

Infiltrate water is the only source of moisture in the soil that helps continue the growth of trees.

transfer of landwater to the oceans

Runoff is the movement of landwater to the oceans, chiefly in the form of rivers, lakes, and streams.

Runoff consists of precipitation that neither evaporates, transpires nor penetrates the surface to become groundwater. Even the smallest streams are connected to larger rivers that carry billions of gallons of water into oceans worldwide.

Excess runoff can lead to flooding, which occurs when there is too much precipitation.

As with all aspects of the water cycle, the interaction between precipitation and surface runoff varies according to time and geography.

Surface runoff is affected by both meteorological factors and the physical geology and topography of the land.

Only about a third of the precipitation that falls over land runs off into streams and rivers and is returned to the oceans. The other two-thirds is evaporated, transpired, or soaks (infiltrates) into ground water. Surface runoff can also be diverted by humans for their own uses.

Type of precipitation (rain, snow, sleet, etc.)

Rainfall intensity

Rainfall amount

Rainfall duration

Distribution of rainfall over the drainage basin

Direction of storm movement

Precipitation that occurred earlier and resulting soil moisture

Other meteorological and climatic conditions that affect evapotranspiration, such as temperature, wind, relative humidity, and season

Land use

Vegetation

Soil type

Drainage area

Basin shape

Elevation

Topography, especially the slope of the land

Drainage network patterns

Ponds, lakes, reservoirs, sinks, etc. in the basin, which prevent or delay runoff from continuing downstream

As precipitation infiltrates into the subsurface soil, it generally forms an unsaturated zone and a saturated zone. In the unsaturated zone, the voids—that is, the spaces between grains of gravel, sand, silt, clay, and cracks within rocks—contain both air and water.

Although a lot of water can be present in the unsaturated zone, this water cannot be pumped by wells because it is held too tightly by capillary forces. The upper part of the unsaturated zone is the soil-water zone.

The soil zone is crisscrossed by roots, openings left by decayed roots, and animal and worm burrows, which allow the precipitation to infiltrate into the soil zone.

Water in the soil is used by plants in life functions and leaf transpiration, but it also can evaporate directly to the atmosphere.

Below the unsaturated zone is a saturated zone where water completely fills the voids between rock and soil particles.

Bringing all the pieces together The hydrologic cycle begins with the evaporation of water from the surface

of the ocean. As moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported around the globe until it returns to the surface as precipitation.

Once the water reaches the ground, one of two processes may occur;

◦ 1) some of the water may evaporate back into the atmosphere or ◦ 2) the water may penetrate the surface and become groundwater.

Groundwater either seeps its way to into the oceans, rivers, and streams, or is released back into the atmosphere through transpiration.

The balance of water that remains on the earth's surface is runoff, which empties into lakes, rivers and streams and is carried back to the oceans, where the cycle begins again.

Lake effect snowfall is good example of the hydrologic cycle at work. Below is a vertical cross-section summarizing the processes of the hydrologic cycle that contribute to the production of lake effect snow. The cycle begins as cold winds (horizontal blue arrows) blow across a large lake, a phenomena that occurs frequently in the late fall and winter months around the Great Lakes.

General Outcomes :Explain the evaporation and evapotranspiration.

Specific Outcomes : State factors influencing evaporation process. Use the Dalton’s law empirical equation to estimate the

rate of evaporation. Explain the method of evaporation measurement using

evaporimeter pan and class A pan. Explain the method to determine evapotranspiration rate.

Factor affecting evaporation process Sunlight Wind Relative humidity Temperature

Empirical Dalton’s Law Equation◦ estimate the evaporation rate prevailing at the

water surface.

Rohwer (1931) C variable value ds eeCE

)00073.0465.1)(073.044.0( pWC W – Hitung panjang halaju angin dalam km/j pada ketinggian 0.15P – Tekanan udara dalam mm raksa pada suhu ºC.

For a plate and a shallow pool of C as,

However for small lakes and dams (reservoir) is

WC 93.015

WC 68.011

Tekanan wap air tepu (es ), boleh ditentukan berdasarkan kepada graf 2.1 sekiranya suhu diketahui samada dalam oF atau oC. Manakala bagi nilai ed pula dapat dikira berdasarkan perkaitannya dengan es

Contoh 2-1 Kira kadar sejatan bagi bulan jun di sebuah

kolam cetek di ladang tebu di Perlis jika suhu dipermukaan air sebagai 25oC, hitung panjang halaju angin 10 km/j, dan hitung panjang suhu dan kelembapan bandingan pada paras ketinggian 7.6 m sebagai masing-masing 30oC dan 60%.

Penyelesaian, Guna persamaan dan tekanan wap air dari rajah (keluk) di

atas. E = (15 + 0.93x10) ( 24 – 32x0.6)

= 116.64 mm/bulan.

a) Evaporation pan

Pan that are commonly used ,square 1.83 m and 610 mm in the water filled up to the level of 550 mm and placed in the soil to the pot rim is extruded as high as 76 mm above the surrounding area.

b) Pan Class A

Standard pot or pan is a round of class A in diameter and 1.22 m depth 254 mm 180 mm deep filled with water and placed on the timber to the base pan 150 mm above ground level.

It is exposed to air in all parts. When it is completed in pairs, they are placed on a stick to tip the pot is 150 mm above where it is close to the surface.

To determine the evapotranspiration, we must take into account the soil surface and plants that are around. While the popular method of measuring evapotranspiration is to use Lisimeter.

Basic principles Lisimeter Lisimeter involves measuring the volume of all incoming and outgoing water through the container that contains a mass of land or land covered with vegetation. The amount of water in and out can also be calculated by using the water balance equation as follows,

dWDETRcIP

There are two types lisimeter commonly used, namely;- weighting

The approach used is the water balance. dsDBIP

- Drainage type

OIBP .

Measurements made every day and potential evapotranspiration can be searched using the following formula;

General Outcomes :Explain the seepage and infiltration

Specific Outcomes : ◦ Define seepage and infiltration.◦ List the factor influencing the seepage rate and

infiltration of water in the soil.◦ Explain the relationship between the infiltration rate

compare to the soil texture.◦ Conduct a practical work to determine the rate of water

infiltration using cylinder infiltrometer.◦ Use Kostiakov equation and soil conservation service

(SCS) equation to estimate the depth of infiltration.

Specific Obj. : ◦ Define seepage and infiltration◦ Explain the factors that influence the rate of

seepage and infiltration of water into the soil ◦ Explain the relationship between infiltration rate

compared to the soil texture ◦ Determine the infiltration rate using cylinder

infiltrometer ◦ Use Kostiakov Equation to estimate infiltration

depth

Seepage and infiltration is the movement of water into the soil. Both mean the same thing, but having a different definition.

Seepage (Resipan) Is the movement of water into the soil vertically and horizontally (side) from sources such as reservoirs and irrigation canals.

Infiltration (Penyusupan)Infiltration is the movement of water vertically from the surface into the soil. Infiltration rate is the maximum rate determination ( penentuan kadar maksima), where the water can enter the land under specific conditions.

1. soil permeability (Kebolehtelapan tanah )2. Water depth in the canal3. Water flow velocity4. bedded (benteng)5. Age of Canal6. Wet parameters

Precipitation: The greatest factor controlling infiltration is the amount and characteristics (intensity, duration, etc.) of precipitation that falls as rain or snow. Precipitation that infiltrates into the ground often seeps into streambeds over an extended period of time, thus a stream will often continue to flow when it hasn't rained for a long time and where there is no direct runoff from recent precipitation.

Soil characteristics and hydraulic conductivity: Some soils, such as clays, absorb less water at a slower rate than sandy soils. Soils absorbing less water result in more runoff overland into streams.

Soil saturation and temperature: Like a wet sponge, soil already saturated from previous rainfall can't absorb much more ... thus more rainfall will become surface runoff.

Land cover: Some land covers have a great impact on infiltration and rainfall runoff. Vegetation can slow the movement of runoff, allowing more time for it to seep into the ground. Impervious surfaces, such as parking lots, roads, and developments, act as a "fast lane" for rainfall - right into storm drains that drain directly into streams. Agriculture and the tillage of land also changes the infiltration patterns of a landscape. Water that, in natural conditions, infiltrated directly into soil now runs off into streams.

Slope of the land: Water falling on steeply-sloped land runs off more quickly and infiltrates less than water falling on flat land.

Evapotranspiration: Some infiltration stays near the land surface, which is where plants put down their roots. Plants need this shallow ground water to grow, and, by the process of evapotranspiration, water is moved back into the atmosphere.

Soil has a capacity to allow water to penetrate the surface through tiny void (liang halus).

The efficiency of soil as a water transfer agent depends on size and the maintenance of this tiny void

Infiltration rate is higher at the beginning of rainfall @ irrigation, and decrease when the soil moisture increased.

Irrigation efficiency of a system is determined by infiltration rate. If the infiltration rate is lower than the water application, part of the supplied moisture is lost through evaporation and runoff.

graph

The popular methods to determine soil infiltration characteristic to get information in the design of irrigation systems

Single-ring infiltrometer Double-ring infiltrometer

Single ring infiltrometer Double ring infiltrometer

Cylinders used 30cm and 60 cm in size with each height 25 cm.

1 2 3 4 5 6 7 8 Reading on

the clock Time

difference Cumulative

time Water level

reading Infiltration

Infiltration rate

Infiltration rate

Cumulative infiltration

Before filling

After filling

Hr min sec min min mm mm mm mm/min mm/hr mm

14 05 0 Start=0

Start=0 100

Start=0 2 (100-92)= 8 (8/2)= 4 240

14 07 0 (0+2)= 2 92 (0+8)= 8 3 (92-85)=7 (7/3)=2.3 138

14 10 0 (2+3)= 5 85 (8+7)= 15 5 (85-75)=10 (10/5)= 2 120

14 15 0 (5+5)= 10 75 100 (15+10)= 25 10 (100-83)=17 (17/10)= 1.7 102

14 25 0 (10+10)= 20 83 (25+17)= 42 10 (83-72)=11 (11/10)= 1.1 66

14 35 0 (20+10)= 30 72 102 (42+11)= 53 10 (102-95)= 7 (7/10)= 0.7 42

14 45 0 (30+10)= 40 95 (53+7)= 60 20 (95-86)= 9 (9/20)= 0.45 27*

15 05 0 (40+20)= 60 86 (60+9)= 69 20 (86-77)= 9 (9/20)= 0.45 27*

15 25 0 (60+20)= 80 77 (69+9)= 78

Column 1 indicates the readings on the clock in hours, minutes and seconds.

Column 1 indicates the readings on the clock in hours, minutes and seconds.

Column 2 indicates the difference in time (in minutes) between two readings.

Column 3 indicates the cumulative time (in minutes); this is the time (in minutes) since the test started.Column 4 indicates the water level readings (in mm) on the measuring rod: before and after filling (see step 5).Column 5 indicates the infiltration (in mm) between two readings; this is the difference in the measured water levels between two readings. How the infiltration is calculated is indicated in brackets.

Column 6 indicates the infiltration rate (in mm/minute); this is the infiltration (in mm; column 5) divided by the difference in time (in minutes, column 2).

Column 7 indicates the infiltration rate (in mm/hour); this is the infiltration rate (in mm/minute, column 6) multiplied by 60 (60 minutes in 1 hour).

Column 8 indicates the cumulative infiltration (in mm); this is the infiltration (in mm) since the test started. How the cumulative infiltration is calculated is indicated in brackets.

Infiltration rate Cum.Infiltration

From plotted graph (Cummulatif Infiltration and Infiltration rate Vs Time), it shown that the graph are parabolic shape and the equation are

cti

Dengan cara memplotkan graf garis lurus iaitu menukar nilai i dan t kepada bentuk log atau melakarkan nilai tersebut di atas graf log-log, maka pekali c dan a boleh didapati melalui kecerunan dan pintasan pada paksi-y bagi graf linear di atas

kadar penyusupan pun dapat ditentukan dengan membuat pembezaan secara matematik persamaan kostiakov

1 ctdt

di