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Presentation on theme: "MENANAM POHON UNTUK MENYUBURKAN BUMI Diabstraksikan: smno.psdl.ppsub.2013."— Presentation transcript:

1 MENANAM POHON UNTUK MENYUBURKAN BUMI Diabstraksikan: smno.psdl.ppsub.2013

2 Diunduh dari: HIDROLOGI HUTAN

3 SIKLUS HIDROLOGI DAN NERACA AIR What happens to precipitation? Water budget: local scale examination of the gains, uses, and losses of water Diunduh dari:

4 LENGAS TANAH Infiltration & percolation Permeability Porosity Zone of aeration: soil water storage plant uptake & transpiration evaporation throughflow Water table Zone of saturation: groundwater flow aquifer Diunjduh dari:

5 NERACA AIR 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

6 DIUNDUH DARI: The hydrological cycle, showing the repartitioning of rainfall into vapor and liquid freshwater flow (modified from Jansson et al. 1999).

7 7 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.

8 DIUNDUH DARI: SIKLUS HARA 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

9 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. Diunduh dari:

10 Diunduh dari: Tree Plantation in South America and the Water Cycle: Impacts and Emergent Opportunities Esteban G. Jobbágy, Germán Baldi, and Marcelo D. Nosetto Forests in Development: A Vital Balance, DOI 10.1007/978-94-007-2576-8_5, © Springer Science+Business Media B.V. 2012 South American tree plantations expand at a rate of 5,000 km2/year favored by increasingly globalized markets and local economic conditions. The main hydrological impacts of these plantations involve shifts in (a) the partition of precipitation inputs between vapour vs. liquid fl uxes (associated to transpiration and canopy interception shifts) and (b) the partition of liquid fluxes between run-off and fast fl ow vs. deep drainage and base fl ow (associated to infi ltration and surface water routing shifts). In sloped terrains global stream fl ow measurements in paired watersheds indicate declining water yields (40% less on average) under plantations vs. native vegetation. These effects are stronger under drier climates, where host vegetation is herbaceous, and where planted trees are eucalypts. In fl at landscapes with native grassland vegetation, tree plantations switch the water balance from positive (net recharge) to negative (net discharge) triggering local salinization. Contrastingly, where native vegetation has been a woodland tree plantation can remediate the undesirable recharge and water table rise/salinization problems brought by agriculture. In degraded rolling (sub)tropical landscapes with intense rainfall inputs and high run-off, tree plantations can increase infi ltration rates, reducing erosion, stabilizing fl ow, but cutting total water yield. As a result of these shifts, erosion can be reduced and the stability and quality of water provision improved, yet these benefits can be erased by large scale clear cutting practices. Context (climate, current vegetation and topography/geology) and design (species, densities, harvesting methods, and scale/pattern) can decide the magnitude and sign of tree plantations effects and need to be carefully considered to get the best ecological outcome of afforestation in the continent.


12 Diunduh dari: http://joa.isa- Soil Water Dynamics and Growth of Street and Park Trees Christian N. Nielsen, Oliver Bühler, and Palle Kristoffersen Arboriculture & Urban Forestry 2007. 33(4):231–245. Soil water dynamics were studied in 100 street tree planting pits and in the soil surrounding five park trees. Volumetric soil water content and stem cross-sectional area increment were measured on both park and street trees. Different levels of irrigation were implemented on the 100 street trees. Winter assessments of soil wetness at field capacity showed that the water retention capacity was lower in street planting pits than in the park soil attributable to the rather coarse substrate used in the planting pits. High variability among street tree planting pits in regard to water retention capacity was determined and may be related to poor standardization of the substrates, but may also be affected by varying drainage conditions. The rate of water loss in the street tree planting pits was very high immediately after rainfall or irrigation and decreased exponentially during the first 10 days after water input. This was attributed to rapid drainage. The water loss rate in the park soil was on average slightly higher than in the nonirrigated control street pits but showed a more linear decrease over time. We concluded that the water loss in the park soil during summer was primarily driven by transpiration of trees (above 10 L/day [2.6 gal/day]), which complies with common Danish forest experience. The relationship between water loss and tree growth was reversed in the street tree planting pits. The street trees did consume water for growth, but growth and transpiration of the street trees were not a noticeably driving mechanism in the planting pit hydrology. The large variation in street tree increment is attributed to the variation among street planting pits in their ability to retain water. The faster the water loss rate, the slower the tree growth. Irrigation did not prevent final depletion of the soil water resource in planting pits, but irrigation elevated the water content for limited periods during the growing season and thereby enhanced tree growth. Besides the obvious possibilities for improved water balance by horizontal and vertical expansion of the rooting zone, we also suggest improving the water retention capacity of planting pit soil by adding clay nodules. Options for continuous monitoring of tree vitality and soil water content to optimize maintenance are discussed.

13 Diunduh dari: Partitioning of soil water among tree species in a Brazilian Cerrado ecosystem Paula C. Jackson, Frederick C. Meinzer, Mercedes Bustamante, Guillermo Goldstein, Augusto Franco,Mercedes BustamanteGuillermo GoldsteinAugusto Franco Philip W. RundelPhilip W. Rundel, Linda Caldas, Erica Igler andLinda CaldasErica Igler Fabio Causin. Tree Physiol (1999) 19 (11): 717-724. Source water used by woody perennials in a Brazilian savanna (Cerrado) was determined by comparing the stable hydrogen isotope composition (δD) of xylem sap and soil water at different depths during two consecutive dry seasons (1995 and 1996). Plant water status and rates of water use were also determined and compared with xylem water δD values. Overall, soil water δD decreased with increasing depth in the soil profile. Mean δD values were –35‰ for the upper 170 cm of soil and –55‰ between 230 and 400 cm depth at the end of the 1995 dry season. Soil water content increased with depth, from 18% near the surface to about 28% at 400 cm. A similar pattern of decreasing soil water δD with increasing depth was observed at the end of the 1996 dry season. Patterns consistent with hydraulic lift were observed in soil profiles sampled in 1995 and 1997. Concurrent analyses of xylem and soil water δD values indicated a distinct partitioning of water resources among 10 representative woody species (five deciduous and five evergreen). Among these species, four evergreen and one deciduous species acquired water primarily in the upper soil layers (above 200 cm), whereas three deciduous and one evergreen species tapped deep sources of soil water (below 200 cm). One deciduous species exhibited intermediate behavior. Total daily sap flow was negatively correlated with xylem sap δD values indicating that species with higher rates of water use during the dry season tended to rely on deeper soil water sources. Among evergreen species, minimum leaf water potentials were also negatively correlated with xylem water δD values, suggesting that access to more readily available water at greater depth permitted maintenance of a more favorable plant water status. No significant relationship between xylem water δD and plant size was observed in two evergreen species, suggesting a strong selective pressure for small plants to rapidly develop a deep root system. The degree of variation in soil water partitioning, leaf phenology and leaf longevity was consistent with the high diversity of woody species in the Cerrado.


15 DIUNDUH DARI: 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.

16 DIUNDUH DARI: 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.

17 DIUNDUH DARI: 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

18 DIUNDUH DARI: 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

19 Diunduh dari: BENEFITS OF TREES Environmental Benefits Trees alter the environment in which we live by moderating climate, improving air quality, conserving water, and harboring wildlife. Climate control is obtained by moderating the effects of sun, wind, and rain. Radiant energy from the sun is absorbed or deflected by leaves on deciduous trees in the summer and is only filtered by branches of deciduous trees in winter. We are cooler when we stand in the shade of trees and are not exposed to direct sunlight. In winter, we value the sun’s radiant energy. Therefore, we should plant only small or deciduous trees on the south side of homes. Wind speed and direction can be affected by trees. The more compact the foliage on the tree or group of trees, the greater the influence of the windbreak. The downward fall of rain, sleet, and hail is initially absorbed or deflected by trees, which provides some protection for people, pets, and buildings. Trees intercept water, store some of it, and reduce storm runoff and the possibility of flooding. Dew and frost are less common under trees because less radiant energy is released from the soil in those areas at night. Temperature in the vicinity of trees is cooler than that away from trees. The larger the tree, the greater the cooling. By using trees in the cities, we are able to moderate the heat-island effect caused by pavement and buildings in commercial areas. Air quality can be improved through the use of trees, shrubs, and turf. Leaves filter the air we breathe by removing dust and other particulates. Rain then washes the pollutants to the ground. Leaves absorb carbon dioxide from the air to form carbohydrates that are used in the plant’s structure and function. In this process, leaves also absorb other air pollutants—such as ozone, carbon monoxide, and sulfur dioxide—and give off oxygen. By planting trees and shrubs, we return to a more natural, less artificial environment. Birds and other wildlife are attracted to the area. The natural cycles of plant growth, reproduction, and decomposition are again present, both above and below ground. Natural harmony is restored to the urban environment.

20 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. DISPOSISI AIR HUJAN

21 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. SIMPANAN AIR HUJAN DALAM TANAH

22 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. INFILTRASI DAN TEKSTUR TANAH

23 Diunduh dari : 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.

24 HIDROLOGI DAS 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.

25 Deskripsi Singkat INFILTRASI 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.

26 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. DIUNDUH DARI:

27 TEKNOLOGI KONSERVASI TANAH 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

28 Diunduh dari: CA2CA5E5CCAE/114437/WesselingStoofetalEffectoftextureOMonhydrologyofco.pdf. THE EFFECT OF SOIL TEXTURE AND ORGANIC AMENDMENT ON THE HYDROLOGICAL BEHAVIOUR OF COARSE-TEXTURED SOILS J. G. Wesseling, C.R.Stoof, C.J.Ritsema, K.Oostindie and L.W.Dekker. Soil Use and Management, September 2009, 25, 274–283 To gain more insight into the hydrological behaviour of coarse-textured soils, the physical properties of artificially created soil mixtures with different texture were determined. The mixtures were prepared according to the specifications of the United States Golf Association (USGA) for constructing putting greens. In addition, the effect of 10 vol.% organic matter addition was studied. The soil moisture retention and hydraulic conductivity relationships of the different mixtures were determined and their hydrological behaviour was studied using the numerical model SoWaM. Both texture and organic matter addition substantially affected the hydraulic properties. Hydraulic conductivity significantly increased with increasing coarseness while moisture retention decreased. On the other hand, organic matter addition reduced saturated hydraulic conductivity by a factor of 10 to 100 and distinctly increased moisture retention capacity. The amounts of total available water were increased by the addition of organic matter between 144% (slightly coarse texture) and 434% (very coarse texture). Results indicate that the mixtures can contain only 2–16% plant available water and therefore need frequent irrigation to maintain plant growth. Addition of organic matter seems a good solution to reduce the irrigation water requirements but it increases the risk of ponding or runoff because of large reductions in the saturated hydraulic conductivity sometimes to below the rate of 3.6 m⁄ day recommended by the USGA..

29 DIUNDUH DARI: Precipitation rains water onto the ground, after that it starts to sink in the ground that is called infiltration.

30 INFILTRASI -- PERKOLASI 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

31 Diunduh dari: Infiltration Characteristics of Soils under Selected Land Use Practices in Owerri, Southeastern Nigeria G.E. Osuji, M.A. Okon, M.C. Chukwuma and I.I. Nwarie World Journal of Agricultural Sciences 6 (3): 322-326, 2010. ISSN 1817- 3047 The infiltration characteristics of soils under four different land use practices were studied in Owerri, Southeastern Nigeria. The land use practices considered were: arable crop land, bush fallow, continuously cultivated land and pineapple orchard. The study aimed at examining the effect of various farming practices on infiltration and determine the degree of relationship between infiltration rates and selected soil properties under different land use practices. The experiment was arranged in a random complete block design which was replicated thrice. The infiltration rates of the soils were measured using the double- ring infiltrometer. Soil samples from these areas were analysed for selected soil physicochemical properties. Data obtained were subjected to analysis of variance, coefficient of variation and correlation and regression analysis. Results showed that bush fallow land had the highest average infiltration of 264 mm/hr while arable crop land experienced the least average rate of 164 mm/hr. From the analysis of variance, there was a highly significant difference (p=0.01) in infiltration rates among treatment means. The coefficient of variation was found to be 3.35%. There were appreciable relationships between steady infiltration rates and soil organic matter, bulk density and total porosity in the order r=0.963, -0.898 and 0.899, respectively. Bulk density, however, was found to be negatively correlated with the infiltration rates, sand and clay%, respectively, however, showed an insignificant relationships (p=0.05) with infiltration rates in the order of r=0.026 and 0.085. It was therefore suggested that marginal lands that are fragile and prone to soil erosion and other soil degradation problems be reverted to bush fallow for organic matter build-up.

32 LENGAS TANAH -- AIR TANAH 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.

33 Diunduh dari: 2009.html. Significance of tree roots for preferential infiltration in stagnic soils B. Lange 1,2, P. Lüescher 1, and P. F. Germann Hydrol. Earth Syst. Sci., 13, 1809-1821, 2009 It is generally recognized that roots have an effect on infiltration. In this study we analysed the relation between root length distributions from Norway spruce (Picea abies (L.) Karst), silver fir (Abies alba Miller), European beech (Fagus sylvatica L.) and preferential infiltration in stagnic soils in the northern Pre-Alps in Switzerland. We conducted irrigation experiments (1 m 2 ) and recorded water content variations with time domain reflectometry (TDR). A rivulet approach was applied to characterise preferential infiltration. Roots were sampled down to a depth of 0.5 to 1 m at the same position where the TDR-probes had been inserted and digitally measured. The basic properties of preferential infiltration, film thickness of mobile water and the contact length between soil and mobile water in the horizontal plane are closely related to root densities. An increase in root density resulted in an increase in contact length, but a decrease in film thickness. We modelled water content waves based on root densities and identified a range of root densities that lead to a maximum volume flux density and infiltration capacity. These findings provide convincing evidence that tree roots in stagnic soils represent the pore system that carries preferential infiltration. Thus, the presence of roots should improve infiltration.

34 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. diunduh dari:

35 Diunduh dari: Vegetation-infiltration relationships across climatic and soil type gradients S. E. Thompson, C. J. Harman, P. Heine, G. G. Katul JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 115, G02023, 12 PP., 2010 The enhancement of infiltration capacity in the presence of vegetation is well documented in arid ecosystems where it can significantly impact the water balance and vegetation spatial organization. To begin progress toward developing a theory of vegetation-infiltration interactions across a wide spectrum of climate regimes, three key questions are addressed: (1) Does vegetation also enhance infiltration capacity in mesic to hydric climates, and if so, what processes contribute to this enhancement? (2) Is there a canonical relationship between vegetation biomass and infiltration rate? and (3) How does the vegetation-infiltration feedback evolve across climatic gradients? To address these three questions, new field data examining biomass-infiltration relationships in different vegetation types in a humid climate and on loamy soils are combined with a meta-analysis of biomass-infiltration relationships from nearly 50 vegetation communities spanning a climatic gradient from hyperarid deserts to the humid tropics and representing a full spectrum of soil types. Infiltration capacity increased as a power law function of aboveground biomass in water-limited ecosystems, but vegetation biomass was not significantly correlated to infiltration capacity in humid climates. Across a climatic gradient from xeric to hydric, the slope of the power law relationship between aboveground biomass and infiltration capacity decreased.

36 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 AIR TANAH – LENGAS TANAH

37 Diunduh dari: 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

38 38 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.

39 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.

40 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.

41 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. INFILTRASI

42 42 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.

43 43 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]

44 44 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]

45 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]

46 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 KONDUKTIVITAS HIDRAULIK TANAH

47 47 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. KEHILANAGAN LENGAS TANAH DARI ZONE AKAR

48 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. KAPASITAS SERAPAN LENGAS TANAH

49 49 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.

50 50 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]

51 51 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]

52 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]

53 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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55 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

56 56 KOMPONEN DAS Genriver 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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59 Diunduh dari: Soil Porosity and Water Infiltration As Influenced by Tillage Practices On UNAAB Soil Kifilideen Lekan OSANYIPEJU Agricultural Engineering, University of Agriculture, Abeokuta, Nigeria October, 2010. The relations between soil pore structure induced by tillage and infiltration play an important role in flow characteristics of water and solutes in soil. The effects of agricultural management practices on soil physical parameters aid the effective sustainability of soils. In this study, three tillage methods common to the study area on porosity and water infiltration were assessed. Tillage treatments include zero tillage (Plot covered with vegetation (conservation tillage)), disc plough (ploughing to the depth of 16 cm, conventional tillage (CT)) and disc harrow (harrowing to a depth of 20 cm, conventional tillage (CT)). Porosity was determined by the core method, water infiltration by the double-ring infiltrometer and hydraulic conductivity from the steady state flow rate. Based on the result obtained there was no significant difference between the zero tillage and disc plough tillage. While there was significant difference between the zero tillage and disc harrow tillage. More so, there was significant difference between the plough tillage and harrow tillage. Based on analysis and comparison of results, it’s indicated high soil sorptivity, porosity and infiltration capacity values for zero tillage follow by disc plough tillage and disc harrow tillage respectively. The bulk density decreased with depth for all the tillage practice. While moisture content and porosity increased with depth for all the tillage practices. Furthermore, it has been found that porosity decreased in the order disc harrow tillage (49.90 %) follow by disc plough tillage (42.62%) and zero tillage (41.17 %) respectively. Meanwhile, infiltration capacity increased in the order zero tillage (24.40 cm/hr) follow by disc plough tillage (32.30 cm/hr) and disc harrow tillage (39.40 cm/hr). It was also observed that there was positive correlation between the infiltration capacity and porosity. The infiltration capacity increased with porosity.

60 Diunduh dari:!Mahe-et-al-J-Hyd-2004- LUCC%20Nakambe.pdf. The impact of land use change on soil water holding capacity and river flow modelling in the Nakambe River, Burkina-Faso Gil Mahea, Jean-Emmanuel Paturel, Eric Servat, Declan Conwayc, Alain Dezetter Journal of Hydrology 300 (2005) 33–43 The annual hydrological regime of the Nakambe River shows substantial changes during the period 1955–1998 with a shift occurring around 1970. From 1970 to the mid-1990s, despite a reduction in rainfall and an increase in the number of dams in the basin, average runoff and maximum daily discharges increased. This paper reviews the hydrological behaviour of the Nakambe River from 1955 to 1998 and examines the potential role of land use change on soil water holding capacity (WHC) in producing the counter-intuitive change in runoff observed after 1970. We compare the results of two monthly hydrological models using different rainfall, potential evapotranspiration andWHC data sets.Model simulations with soilWHC values modified over time based upon historical maps of land use, are compared against simulations with a constant value forWHC. The extent of natural vegetation declined from 43 to 13% of the total basin area between 1965 and 1995, whilst the cultivated areas increased from 53 to 76% and the area of bare soil nearly tripled from 4 to 11%. The total reduction in WHC is estimated to range from 33 to 62% depending on the method used, either considering that the WHC values given by the FAO stand for the environmental situation in 1965 or before. There is a marked improvement in river flow simulation using the time-varying values of soilWHC. The paper ends with a discussion of the role of other factors such as surface runoff processes and groundwater trends in explaining the hydrological behaviour of the Nakambe River.

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