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Presentation on theme: "1 PENANAMAN POHON MELESTARIKAN SUMBER MATA AIR Soemarno - pslp ppsub 2010 BAHAN KAJIAN MANAJEMEN EKOSISTEM."— Presentation transcript:


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3 3 Peran pohon dalam siklus air

4 4 Provide social, ecological, and economic benefits Their leaves and roots clean the air we breathe and the water we drink Trees: The Original Multi-taskers Their beauty inspires writers and other artists.

5 5 Save Energy Improve air quality Extend life of paved surfaces Increase traffic safety Increase real estate values Increase sociological benefits Protect our water resources Benefits of Trees in Urban Areas

6 6 All water is part of this cycle

7 7 Storm Water and the Hydrologic Cycle Urbanization dramatically alters the hydrologic cycle –Increases runoff –Increases flooding frequency –Decreases infiltration and groundwater recharge Nationwide impervious surfaces have increased by 20% in the past 20 years

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9 9 More Trees Means Less Runoff Some Statistics Fayetteville, Arkansas: increasing tree canopy from 27- 40% reduced their storm water runoff by 31% South Miami residential study found that a 21% existing tree canopy reduces the storm water runoff by 15% For every 5% of tree cover added to a community, storm water is reduced by approximately 2%

10 10 How Do Trees Effect Stormwater? Above ground effects: –Interception, evaporation and absorption of precipitation Ground surface effects: –Temporary storage Below ground effects: –Infiltration, permeation and filtration

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12 12 Above Ground Effects Intercept rainwater on leaves, branches and trunks – slowing its movement Evaporation of some of this intercepted precipitation of the tree surfaces Absorption of a small portion into leaves or stems

13 13 Leaf litter and other organic matter can hold precipitation and stemflow on a site, reducing the amount and peak rates of runoff Ground Surface Effects Roots and trunk bases of mature trees tend to create hollows and hummocks on the ground

14 14 Below Ground Effects Organic material from leaf litter and other tree detritus tends to increase infiltration rates by increasing pore spaces in soil Organic material also increases the moisture-holding capacity of these sites Root mats of trees also tend to break up most soils further improving infiltration and moisture-holding capacity

15 15 Below Ground Effects cont Deep roots tend to improve the rates of percolation of water from upper soil horizons into lower substrates Trees take up water through their roots that is eventually transpired onto leaf surfaces and evaporated Tree roots act as natural pollution filters (biofilters) using nitrogen, phosphorus and potassium

16 16 EPA’s Tree Canopy Target Goals Set to protect a community’s green infrastructure and maximize the environmental benefits For metropolitan areas east of the Mississippi –Average tree cover for all land use 40% –Suburban residential 50% –Urban residential 25% –Central business districts 15%

17 17 Complications?

18 18 Complicating Factors Presence of soil compaction Presence of soil textural discontinuity –Has the site been disturbed in the past? Management of the ground surface –Is litter layer removed? –Is soil surface exposed in winter? –How much of the surface is like a natural forest? (number and size of trees)

19 19 Water Movement in Soils Forces affecting the energy of soil water –Matric force (absorption and capillary) –Gravity –Osmotic forces Field Capacity is the amount of water held in the soil after gravitational water had drained away Movement of water is the soil is controlled : –Gravitational forces if saturated –Matric forces if unsaturated

20 20 Soil Factors Influencing Infiltration Infiltration is the mode of entry of all water into the soil Rate of infiltration determined: –Initial water content –Surface permeability –Internal characteristics of the soil Intensity and duration of rainfall Temperature of soil and water

21 21 Soil Factors Influencing Infiltration cont. Microrelief under trees provides catchment basins during heavy rains Removal of litter layer reduces the infiltration rate Forest soils have a high percentage of macropores The frost type found in forest soils promotes infiltration year-long Soil compaction reduces the infiltration rate

22 22 Importance of the Litter Layer Absorbs several times its own weight Breaks the impact of raindrops Prevents agitation of the mineral soil Discourages formation of surface crusts Increases soil biotic activity Increases incorporation of organics Slows down lateral movement of water

23 23 Affect of Micropores in the Soil Develop in old root channels or from burrows and tunnels made by insects, worms or other animals Lead to better soil structure Increases organic matter incorporation Increases percolation rates and root penetration

24 24 Soil Frost Types Granular –Small frost crystals intermingled with soil particles –Found in woodland soils with litter –May be more permeable than unfrozen soil Honeycomb –Has loose porous structure –Found in highly aggregated soils and also formed in organic layers and litter layers

25 25 Source and fate of water added to a soil system. The proportion of the soil occupied by water and air is referred to as the pore volume. The pore volume is generally constant for a given soil layer but may be altered by tillage and compaction. The ratio of air to water stored in the pores changes as water is added to or lost from the soil. Water is added by rainfall or irrigation. Water is lost through surface runoff, evaporation (direct loss from the soil to the atmosphere), transpiration (losses from plant tissue), and either percolation (seepage into lower layers) or drainage.

26 26 Components of Ground Water Use and Sources of Recharge There is a substantial amount of ground water recharge from surface water and ground water used to irrigate agricultural crops. Some of the irrigation water flowing in unlined ditches and some of the water that is applied to irrigate crops infiltrates into the soil, percolates through the root zone and recharges the ground water basins

27 27 Ground water Ground water occupies the zone of saturation. Ground water moves downward through the soil by percolation and then toward a stream channel or large body of water as seepage. The water table separates the zone of saturation from the zone of aeration. The water table fluctuates with moisture conditions, during wet times the water table will rise as more pore spaces are occupied with water. Ground water is found in aquifers, bodies of earth material that have the ability to hold and transmit water. Aquifers can be either unconfined or confined. Unconfined (open) aquifers are "connected" to the surface above.

28 28 Aquifers replenish their supply of water very slowly. The rate of ground water flow depends on the permeability of the aquifer and the hydraulic gradient. Permeability is affected by the size and connectivity of pore spaces. Larger, better connected pore spaces creates highly permeable earth material. The hydraulic gradient is the difference in elevation between two points on the water table divided by the horizontal distance between them. The rate of ground water flow is expressed by the equation: Ground water flow rate = permeability X hydraulic gradient Groundwater flow rates are usually quite slow. Average ground water flow rate of 15 m per day is common. Highly permeable materials like gravels can have flow velocities of 125 m per day.

29 29 Ground water in an aquifer is under pressure called hydrostatic pressure. Hydrostatic pressure in a confined aquifer pushes water upward when a well is drilled into the aquifer. The height to which the water rises is called the peizometeric surface. If the hydrostatic pressure is great enough to push the peizometeric surface above the elevation of the surface, water readily flows out as an artesian well.

30 30 Following an infiltration event, in which the entire soil profile becomes saturated with water (indicated by a solid vertical line corresponding to a water saturation of 1.0), water will drain from the soil profile primarily under the influence of gravity (i.e., the pressure gradient is negligible). Assuming that no additional water enters the system, the soil water saturation profile at static equilibrium (dashed line) will decrease from a value of 1.0 in the saturated zone (groundwater and capillary fringe) to a value corresponding to field capacity below the root zone. In effect, the soil water profile is analogous to a soil water retention (pressure-saturation) curve. Hence, the solid and dashed lines represent the limits in water content (saturation) between which soil water percolation occurs in soils overlying an unconfined aquifer.

31 31 Water is recharged to the ground- water system by percolation of water from precipitation and then flows to the stream through the ground-water system.

32 32 Water pumped from the ground- water system causes the water table to lower and alters the direction of ground-water movement. Some water that flowed to the stream no longer does so and some water may be drawn in from the stream into the ground-water system, thereby reducing the amount of streamflow..

33 33 Contaminants introduced at the land surface may infiltrate to the water table and flow towards a point of discharge, either the well or the stream. (Not shown, but also important, is the potential movement of contaminants from the stream into the ground- water system.)

34 34 Water-level declines may affect the environment for plants and animals. For example, plants in the riparian zone that grew because of the close proximity of the water table to the land surface may not survive as the depth to water increases. The environment for fish and other aquatic species also may be altered as the stream level drops.

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36 36 The fate of applied water can be better understood if the total hydrologic cycle is understood first. The hydrologic cycle, illustrated in Figure 1, describes the movement of water through its different forms and locations. Important processes in the hydrologic cycle are: 1. Evaporation -the transformation of liquid water into water vapor from free water surfaces. 2. Precipitation (rain or snow). 3. Runoff -water moving overland or in a river or stream. 4. Infiltration -the movement of water into the soil. 5. Percolation -the movement of water through the soil. 6. Freezing - liquid water turning into ice 7. Thawing - melting of ice 8. Transpiration - the movement of water vapor out through plant/animal tissue surfaces into the atmosphere.

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38 38 Forests and the Hydrologic Cycle The surface water in a stream, lake, or wetland is most commonly precipitation that has run off the land or flowed through topsoils to subsequently enter the waterbody. If a surficial aquifer is present and hydraulically connected to a surface-water body, the aquifer can sustain surface flow by releasing water to it. In general, a heavy rainfall causes a temporary and relatively rapid increase in streamflow due to surface runoff. This increased flow is followed by a relatively slow decline back to baseflow, which is the amount of streamflow derived largely or entirely from groundwater. During long dry spells, streams with a baseflow component will keep flowing, whereas streams relying totally on precipitation will cease flowing. Generally speaking, a natural, expansive forest environment can enhance and sustain relationships in the water cycle because there are less human modifications to interfere with its components. A forested watershed helps moderate storm flows by increasing infiltration and reducing overland runoff. Further, a forest helps sustain streamflow by reducing evaporation (e.g., owing to slightly lower temperatures in shaded areas). Forests can help increase recharge to aquifers by allowing more precipitation to infiltrate the soil, as opposed to rapidly running off the land to a downslope area.

39 39 Forests and prairies rarely yield runoff regardless of steepness, even when frozen Forested areas provide storm water protection and protect the quantity and quality of groundwater Implications of Frost Types

40 40 Groundwater –Surface Water Flows

41 41 Black Earth Creek Study Black Earth Creek receives 80% of its water from groundwater Main recharge occurs in spring and fall Recharge from the agricultural uplands is highly variable Forested slopes are significant recharge areas Wooded hill slopes generate no significant runoff

42 42 Effects are greatest during the growing season Effects are greatest on sites whose soils are relatively impermeable Trees and Storm Water: Conclusions

43 43 The impact of urban trees on hydrology is extremely variable and complex, in general increases in tree cover and tree size over a site will result in reduced total runoff amounts and peak runoff rates.

44 44 Trees and Storm Water: Trees have a relatively greater effect on smaller storm runoff amounts than on large storm events Surface and below- ground effects on runoff are much more significant than the above-ground effects All of the effects on runoff are greatest when urban trees are large and well- established on undisturbed sites

45 45 Contact Information: Mindy Habecker Dane County UW-Extension 224-3718

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48 48 Typical root systems are made up of a combination of four types of roots: major lateral roots sinker roots woody feeder roots non-woody feeder roots.

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50 50 ban/landscape- manual.shtml

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52 52 Tree and Root System on Bank of Darling River, Kinchega National Park, Outback, New South Wales, Australia

53 53 Fir-Roo...

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56 56 A model illustrating fluxes of sulphur in a forest ecosystem

57 57 Schematic illustration of the biogeochemical processes of importance in long-term research of a watershed (Swank, 1986).

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62 62 Four-Way Collaboration The Water Balance Model includes a tree canopy module so that the rainfall interception benefits of trees in the urban environment can be quantified. To populate the module with local data, a four-way collaboration has been established under the umbrella of the Inter-Governmental Partnership (IGP) that developed the Water Balance Model. The Greater Vancouver Regional District and Ministry of Community Services are providing funding, and the University of British Columbia and District of North Vancouver are making in-kind contributions in carrying out the applied research project. The District of North Vancouver is acting on behalf of the IGP in leading this on-the-ground initiative.Water Balance Model

63 63 Tree canopy interception is the process of storing precipitation temporally in the canopy and releasing it slowly to the ground and back to the atmosphere. It is an important component of the water balance, easily accounting for up to 35% of gross annual precipitation. Removing trees will in general decrease interception and thus increase annual runoff and rainwater runoff. Vegetation also reduces rainfall intensity due to the temporal storage effect.

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65 65 SOIL WATER infiltration & percolation permeability porosity Zone of aeration: soil water storage plant uptake & transpiration evaporation throughflow Water table Zone of saturation: groundwater flow aquifer

66 66 HYDROLOGIC CYCLE & WATER BUDGETS What happens to precipitation? Water budget: local scale examination of the gains, uses, and losses of water

67 67 WATER BALANCE Gains: precipitation Soil moisture storage Losses: utilization and evapotranspiration actual evapotranspiration (AE) potential evapotranspiration (PE) Simple water balance: moisture abundant environments P > PE and therefore AE = PE moisture limited environments P < PE and therefore AE < PE seasonal moisture environments

68 68 www.ecologyandsociety. org/vol3/iss2/art5/ The hydrological cycle, showing the repartitioning of rainfall into vapor and liquid freshwater flow (modified from Jansson et al. 1999).

69 69 INVISIBLE GREEN WATER VAPOR AND VISIBLE BLUE LIQUID WATER It is distinguished between water vapor flows and liquid water flows. In the literature on water and food production, water vapor and liquid water are sometimes called green water and blue water, respectively. Both concepts provide useful tools for the analysis of local, regional, and global flows in the hydrologic cycle. Liquid (blue) water flow is the total runoff originating from the partitioning of precipitation at the land surface (forming surface runoff ) and the partitioning of soil water (forming groundwater recharge). Water vapor (green) is the return flow of water to the atmosphere as evapotranspiration (ET), which includes transpiration by vegetation and evaporation from soil, lakes, and water intercepted by canopy surfaces. We regard ET as the result of the work of the whole ecosystem, including the resilience it needs for securing the generation of ecosystem services in the long run.

70 70 1Eco2.htm Nutrient cycle We already know trees rely on nutrients like phosphorous and nitrogen for healthy growth and reproduction. Throughout a trees life stages, they constantly use and return nutrients to the soil. Nutrient cycles regularly transform nutrients from the non-living environment (air, soil, water, rocks) to the living environment and then back again

71 71 Water cycle Water is constantly cycling. The water cycle collects, purifies, and distributes the world�s water. Without the water cycle, life on earth would be impossible. Trees and plants are part of this water cycle. Transpiration is the controlled evaporation process by which plants lose H2O through the pores in their leaf structures. A full-grown tree can transpire hundreds of gallons of water a day during growing season.

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73 73 www.fastest-growing-

74 74 Water deeply rather than frequently. Because most tree roots are found in the upper 18 - 24 inches of the soil, this is the zone that should be wetted up in each irrigation cycle. Each deep irrigation will meet a tree's water needs for between 10 days to 4 weeks during the hottest part of the summer, depending on the tree species and soil type.

75 75 www.cmhc- Trees require water for many biological functions, but the function requiring the greatest quantity of water is transpiration. Transpiration is the movement of water vapour from the leaves of plants to the atmosphere. The soil in which trees grow is the reservoir from which tree roots draw water.

76 76 As a general rule of thumb, management of trees near buildings in sensitive clay soils should begin no later than when the height of the tree is equal to the horizontal distance of the tree to the building

77 77 Tree Facts - Environmental Benefits Trees intercept and slow storm water, decreasing the likelihood of flooding and erosion, and improving water quality Large trees have a greater benefit in terms of reducing pollution than small trees Trees, shrubs, hedges and grasses have a positive effect on the environment by the transpiration of water and the emission of oxygen by photosynthesis Plantings around buildings are a proven method of reducing the demand for artificial heating and cooling with a resultant, and important, lower use of fossil fuels. Greenery provides ‘white noise’ reducing the effects of man-made sounds

78 78 Air hujan yang jatuh ke tanah tidak seluruhnya langsung mengalir sebagai air permukaan, tetapi ada yang terserap oleh tanah. Peresapan air ke dalam tanah pada umumnya terjadi melalui dua tahapan, yaitu infiltrasi dan perkolasi. Infiltrasi adalah gerakan air menembus permukaan tanah masuk ke dalam tanah. Perkolasi adalah proses penyaringan air melalui pori-pori halus tanah sehingga air bisa meresap ke dalam tanah.

79 79 Kuantitas air yang mampu diserap tanah sangat tergantung beberapa faktor, yaitu: jumlah air hujan, kondisi fisik tanah seperti bobot isi, infiltrasi, porositas dan struktur tanah, jumlah tumbuh-tumbuhan serta lapisan yang tidak dapat ditembus oleh air. Terbentuknya sumber- sumber air di alam mengalami serangkaian proses. Air hujan jatuh ke tanah kemudian meresap ke dalam tanah. Sebelum mencapai jenuh, air masih dapat diserap oleh tanah. Sampai di kedalaman tertentu, air tersebut tertahan oleh lapisan batu-batuan (lapisan kedap air), yang membendung air sehingga tidak terus meresap ke bawah sehingga membentuk air tanah. Jika telah mengalami jenuh, air yang jatuh ke permukaan tanah akan dialirkan sebagai air permukaan.

80 80 Secara mudah ilfiltrasi digambarkan seperti disebalah ini. Kalau tanahnya berbutir kasar dan berpori-pori bagus, maka air akan terserap. Ketika air hujan menjatuhi tanah lanau yg lebih halus, maka kapasitas ilfiltrasinya berkurang banyak. Demikian juga ketika air hujan turun tepat diatas lempung, ya lebih sulit lagi terserap.

81 81 1101.htm Saat terjadinya hujan, air dapat masuk ke dalam tanah (infiltrasi) atau mengalir di permukaan tanah (limpasan permukaan / surface run- off). Air dalam tanah yang terikat oleh pori- pori dan mineral tanah, ada yang dapat dimanfaatkan oleh tanaman sebagai air tersedia, menguap dari permukaan tanah atau mengalir di permukaan atau ke dalam tanah (perkolasi), dan tersimpan dalam tanah sebagai air tanah.

82 82 Telah diketahui bahwa Konsep daur hidrologi DAS menjelaskan bahwa air hujan langsung sampai ke permukaan tanah untuk kemudian terbagi menjadi air larian, evaporasi dan air infiltrasi, yang kemudian akan mengalir ke sungai sebagai debit aliran.

83 83 Deskripsi Singkat Infiltrasi dari segi hidrologi penting, karena hal ini menandai peralihan dari air permukaan yang bergerak cepat ke air tanah yang bergerak lambat dan air tanah. Kapasitas infiltrasi suatu tanah dipengaruhi oleh sifat-sifat fisiknya dan derajat kemampatannya, kandungan air dan permebilitas lapisan bawah permukaan, nisbi air, dan iklim mikro tanah. Air yang berinfiltrasi pada sutu tanah hutan karena pengaruh gravitasi dan daya tarik kapiler atau disebabkan juga oleh tekanan dari pukulan air hujan pada permukaan tanah.

84 84 Sirkulasi air yang berpola siklus itu tidak pernah berhenti dari atmosfir ke bumi dan kembali ke atmosfir melalui kondensasi, presipitasi, evaporasi, dan transpirasi.Pemanasan air samudera oleh sinar matahari merupakan kunci proses siklus hidrologi tersebut dapat berjalan secara kontinu. Air berevaporasi, kemudian jatuh sebagai presipitasi dalam bentuk hujan, salju, hujan batu, hujan es dan salju (sleet), hujan gerimis atau kabut. Pada perjalanan menuju bumi beberapa presipitasi dapat berevaporasi kembali ke atas atau langsung jatuh yang kemudian diintersepsi oleh tanaman sebelum mencapai tanah. Setelah mencapai tanah, siklus hidrologi terus bergerak secara kontinu dalam tiga cara diantaranya melaui kondensasi, presipitasi, evaporasi dan transpirasi.

85 85 A number of management options have been tried to conserve water in the soil, improve structural stability and increase productivity. The available management options can be grouped into three categories: a. Tillage based systems b. Organic systems c. Biological systems

86 86 m/2009/11/water- cycle.html Precipitation rains water onto the ground, after that it starts to sink in the ground that is called infiltration.

87 87 Infiltrasi/Perkolasi ke dalam tanah Adalah Air bergerak ke dalam tanah melalui celah- celah dan pori-pori tanah dan batuan menuju muka air tanah. Air dapat bergerak akibat aksi kapiler atau air dapat bergerak secara vertikal atau horizontal dibawah permukaan tanah hingga air tersebut memasuki kembali sistem air permukaan

88 88 Air tanah merupakan air yang mengisi rongga- rongga batuan di bawah permukaan tanah pada zone jenuh air. Kondisi air tanah sangat beragam dan pada musim tertentu akan mengalami perubahan dan faktor tersebut juga merupakan faktor cuaca dan iklim serta faktor radiasi terestrial. Radiasi yang masuk pada tanah pada musim hujan dan musim kering akan sangat berbeda dan suhu yang terjadi juga akan mengalami perubahana dengan daya serap tanah akan berbeda.

89 89 Sebagian dari air tanah dihisap oleh tumbuh- tumbuhan melalui daun- daunan lalu menguapkan airnya ke udara (transpiration). Air yang mengalir di atas permukaan menuju sungai kemungkinan tertahan di kolam, selokan dan sebagainya (surface detention), ada juga yang sementara tersimpan di danau, tetapi kemudian menguap atau sebaliknya sebagian air mengalir di atas permukaan tanah melalui parit, sungai, hingga menuju ke laut ( surface run off ), sebagian lagi infiltrasi ke dasar danau- danau dan bergabung di dalam tanah sebagi air tanah yang pada akhirnya ke luar sebagi mata air.

90 90 AIR TANAH Air tanah adalah air yang terdapat dalam pori-pori tanah atau pada celah- celah batuan. Air tanah terbentuk dari air hujan. Pada saat turun hujan, sebagian titik-titik air meresap ke dalam tanah (infiltrasi). Air hujan yang masuk itu yang menjadi adangan air tanah. Volume air yang meresap ke dalam tanah tergantung pada jenis lapisan batuannya. Berdasarkan kenyataan tersebut terdapat pula dua jenis batuan utama, yaitu lapisan kedap (impermiable) dan lapisan tanah tidak kedap air (permeable) Kadar pori lapisan kedap atau tak tembus air sangat kecil, sehingga kemampuan untuk meneruskan air juga kecil. Contoh lapisan kedap, yaitu geluh, napal, dan lempung. Sedangkan kadar pori lapisan tak kedap air atau tembus air cukup besar. Oleh karena itu, kemampuan untuk meneruskan air juga besar. Contoh lapisan tembus air, yaitu pasir, padas, krikil dan kapur. Kita akan lihat bersama gambar lapisan kedap dan lapisan tak kedap pada air tanah di halaman berikutnya

91 91 ogy.html Water Balance Components Inflow: Precipitation Import defined as water channeled into a given area. Groundwater inflow from adjoining areas. Outflow: Surface runoff outflow Export defined as water channeled out of the same area. Evaporation Transpiration Change in Storage: This occurs as change in: Groundwater Soil moisture Surface reservoir water and depression storage Detention Storage

92 92 Hydrological Systems A hydrologic system is as a structure or volume in space, surrounded by a boundary, that accepts water and other inputs, operates on them internally, and produces them as outputs.

93 93 aXRlbV9pZD02Mg== Water supply to the roots, infiltration, runoff, percolation and redistribution of water in a one- dimensional profile are derived from hydraulic characteristics and moisture storage capacity of the soil.

94 94 chapt6.htm The processes directly affecting the root zone soil moisture content can be defined as: Infiltration: i.e. transport from the soil surface into the root zone; Evaporation: i.e. the loss of soil moisture to the atmosphere; Plant transpiration: i.e. loss of water from the interior root zone; Percolation: i.e. downward transport of water from the root zone to the layer below the root zone; Capillary rise: i.e. upward transport into the rooted zone.

95 95 Preliminary infiltration The infiltration rate depends on the available water and the infiltration capacity of the soil. If the actual surface storage is less then or equal to 0.1 cm, the preliminary infiltration capacity is simply described as: Where INp : Preliminary infiltration rate[cm d-1] FI : Maximum fraction of rain not infiltrating during time step t[-] CI : Reduction factor applied to FI as a function of the precipitation intensity[-] P : Precipitation intensity[cm d-1] Ie : Effective irrigation[cm d-1] SSt : Surface storage at time step t [cm] Dt : Time step[d] The maximum fraction of rain not infiltrating during time step t, FI can be either set to a fixed value or assumed to be variable by multiplying FI with a precipitation dependent reduction factor CI which is maximum for high rainfall and will be reduced for low rainfall. The user should provide FI. The CI table is included in the model and is assumed to be fixed.

96 96 The calculated infiltration rate is preliminary, as the storage capacity of the soil is not yet taken into account. If the actual surface storage is more than 0.1 cm, the available water which can potentially infiltrate, is equal to the water amount on the surface (i.e. supplied via rainfall/irrigation and depleted via evaporation): Where INp : Preliminary infiltration rate[cm d-1] P : Precipitation intensity[cm d-1 Ie : Effective irrigation[cm d-1] Ew : Evaporation rate from a shaded water surface[cm d-1] SS : Surface storage at time step t [cm] Dt :Time step[d] However, the infiltration rate is hampered by the soil conductivity and cannot exceed it. Soil conductivity is soil specific and should be given by the user.

97 97 Adjusted infiltration Total water loss from the root zone can now be calculated as the sum of transpiration, evaporation and percolation. The sum of total water loss and available pore space in the root zone define the maximum infiltration rate. The preliminary infiltration rate cannot exceed this value. The maximum possible infiltration rate is given by: Where: INmax :Maximum infiltration rate[cm d-1] qmax :Soil porosity (maximum soil moisture)[cm3 cm-3] Qt :Actual soil moisture content[cm3 cm-3] RD :Actual rooting depth[cm] Dt :Time step[d]Ta:Actual transpiration rate[cm d-1 Es :Evaporation rate from a shaded soil surface [cm d-1] Perc :Percolation rate from root zone to lower zone[cm d-1]

98 98 PERKOLASI If the root zone soil moisture content is above field capacity, water percolates to the lower part of the potentially rootable zone and the subsoil. A clear distinction is made between percolation from the actual rootzone to the so-called lower zone, and percolation from the lower zone to the subsoil. The former is called Perc and the latter is called Loss. The percolation rate from the rooted zone can be calculated as: Where Perc : Percolation rate from the root zone to the lower zone[cm d-1] Wrz : Soil moisture amount in the root zone [cm] Wrz,fc Equilibrium soil moisture amount in the root zone [cm] Dt : Time step[d] Ta : Actual transpiration rate [cm d-1] Es : Evaporation rate from a shaded soil surface [cm d-1]

99 99 The equilibrium soil moisture amount in the root zone can be calculated as the soil moisture content at field capacity times the depth of the rooting zone: Where Wrz,fc : Equilibrium soil moisture amount in the root zone[cm] Qfc : Soil moisture content at field capacity[cm3 cm-3] RD : Actual rooting depth[cm]

100 100 The percolation rate and infiltration rate are limited by the conductivity of the wet soil, which is soil specific and should be given by the user. Note that the percolation from the root zone to the lower zone can be limited by the uptake capacity of the lower zone. The value calculated is preliminary and the uptake capacity should first be checked. The percolation from the lower zone to the subsoil, the so-called Loss, should take the water amount in the lower zone into account. If the water amount in the lower zone is less than the equilibrium soil moisture amount, a part of the percolating water will be retained and the percolation rate will be reduced. Water loss from the lower end of the maximum root zone can be calculated as: Where Loss :Percolation rate from the lower zone to the subsoil[cm d-1] Perc :Percolation rate from root zone to lower zone (see eq. 6.21)[cm d-1] Wlz :Soil moisture amount in the lower zone [cm] Wlz,fc :Equilibrium soil moisture amount in the lower zone [cm] Dt :Time step

101 101 Water loss from the potentially rootable zone, is also limited by the maximum percolation rate of the subsoil, which is soil specific and should be provided by the user. The equilibrium soil moisture amount in the lower zone can be calculated as the soil moisture content at field capacity times the root zone depth: Where Wrz,fc : Equilibrium soil moisture amount in the lower zone[cm] Qfc :Soil moisture content at field capacity[cm3 cm-3] RDmax :Maximum rooting depth[cm] RD :Actual rooting depth[cm] For rice an additional limit of five percent of the saturated soil conductivity is set to account for puddling (a rather arbitrary value, which may be easily changed in the program). The saturated soil conductivity and is calculated with pF= -1.0 (i.e. a hydraulic head of 0.1 cm). The percolation rate from the lower zone to the sub soil is not to exceed this value (van Diepen et al., 1988). The value calculated should be regarded as preliminary; the storage capacity of the receiving layer may become limiting.

102 102 The storage capacity of the lower zone, also called the uptake capacity, is the amount of air plus the loss. It can de defined as: Where UP :Uptake capacity of lower zone[cm d-1] RDmax :Maximum rooting depth[cm] RD :Actual rooting depth[cm] Wlz :Soil moisture amount in lower zone[cm] Qmax :Soil porosity (maximum soil moisture)[cm3 cm-3] Dt :Time step[d] Loss :Percolation rate from the lower zone to the subsoil[cm d-1] Percolation to the lower part of the potentially rootable zone can not exceed the uptake capacity of the lower zone. Therefore the percolation rate is set equal to the minimum of the calculated percolation rate and the uptake.

103 103 LIMPASAN PERMUKAAN : Surface runoff Surface runoff is also taken into account by defining a maximum value for surface storage. If the surface storage exceeds this value the exceeding water amount will run off. Surface storage at time step t can be calculated as: Where SSt : Surface storage at time step t[cm d-1] P : Precipitation intensity[cm d-1] Ie : Effective irrigation rate[cm d-1] Ew : Evaporation rate from a shaded water surface[cm d-1] IN : Infiltration rate (adjusted)[cm d-1] Surface runoff can be calculated as: Where SRt:Surface runoff at time step t[cm] SSt:Surface storage at time step t[cm] SSmax:Maximum surface storage[cm] SSmax is an environmental specific variable and should be provided by the user.

104 104 Rates of change and root extension The rates of change in the water amount in the root and lower zone are calculated straightforward from the flows found above: Where DWrz :Change of the soil moisture amount in the root zone[cm] DWlz :Change of the soil moisture amount in the lower zone[cm] Ta :Actual transpiration rate[cm d-1] Es :Evaporation rate from a shaded soil surface[cm d-1]; IN :Infiltration rate[cm d-1] Perc :Percolation rate from root zone to lower zone[cm d-1] Loss :Percolation rate from lower zone to sub soil[cm d-1]; Dt :Time step[d] Due to extension of the roots into the lower zone, extra soil moisture becomes available, which can be calculated as: Where RDt :Rooting depth at time step t[cm] RDt-1:Rooting depth at time step t-1[cm] RDmax:Maximum rooting depth[cm] Wlz:Soil moisture amount in the lower zone [cm] DWrz:Change of the soil moisture amount in the root zone[cm] DWlz:Change of the soil moisture amount in the lower zone[cm]

105 105 The actual water amount in the root zone and in the lower zone can be calculated according to: Where: Wrz,t : Soil moisture amount in the root zone at time step t[cm] Wlz,t : Soil moisture amount in the lower zone at time step t[cm] Wrz,t-1: Soil moisture amount in the root zone at time step t-1[cm] Wlz,t-1: Soil moisture amount in the lower zone at time step t-1[cm] DWrz : Rate of change of the soil moisture amount in the root zone[cm] DWlz : Rate of change of the soil moisture amount in the lower zone[cm]

106 106 Actual soil moisture content The actual soil moisture content can now be calculated according to : Where qt : Actual soil moisture content at time step t [cm3 cm-3] Wrz,t : Soil moisture amount in the root zone at time step t [cm] RD : Actual rooting depth [cm]

107 107 of-soil-erosion Effects of Deforestation 1) Percolation and ground water recharge has decreased. 2) Floods and drought have become more frequent. 3) Soil erosion has increased. 4) Pattern of rainfall has changed. 5) Land slides and avalanches are on the increase. 6) Climate has become warmer in the deforested region due to lack of humidity added by the plants. 7) Consumption of CO2 and production of O2 is adversely affected. 8) Man has been deprived of the benefits of trees and animals. 9) Extinction of many species of plants and animals, still not discovered by scientists. 10) Shortage of fuel

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109 109 GenRiver: Generic River model on river flow Overview of the GenRiver model; the multiple subcatchments that make up the catchment as a whole can differ in basic soil properties, land cover fractions that affect interception, soil structure (infiltration rate) and seasonal pattern of water use by the vegetation. The subcatchment will also typically differ in ‘routing time' or in the time it takes the streams and river to reach the observation point of main interest

110 110 Genriver Components GenRiver model consists of several sectors, which are related to one another. Those sectors are: Water Balance is a main sector that calculating the input, output, and storage changes of water in the systems. Some components which are in this sector, rainfall, interception, infiltration, percolation, soil water, surface flow, soil discharge, deep infiltration, ground water area and base flow Stream Network is a sector that estimating the flow of water from the river to the final outlet. Some components which are in this sector, total ttream in flow, routing time, direct surface flow, delay surface flow, river flow to final outlet. Land CoverÂ, Subcatachment Parameter is a sector stired constant parameters that control to the changes of water balance, landcover and stream network.

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