Evaluation of Soil Erosion and Sedimentation Rates of Pangasugan Watershed in Pangasugan Baybay City, Leyte

A Thesis Manuscript

Presented tothe Faculty of the

Institute of Tropical Ecology and Environmental ManagementCollege of Forestry and Environmental Science

Visayas State UniversityVisca, Baybay City, Leyte

In Partial FulfillmentOf the Requirement for the Degree of

Bachelor of Science in Environmental Management

WILBERT ACEBO AUREOApril 2013

Institute of Tropical Ecology and Environmental ManagementCollege of Forestry and Environmental Science

Visayas State UniversityVisca, Baybay City, Leyte

Envi 200 AUDERGRADUATE THESIS

APPROVAL SHEET

Title: EVALUATION OF SOIL EROSION AND SEDIMENTATION RATES OF PANGASUGAN WATERSHED IN PANGASUGAN BAYBAY CITY, LEYTE

Author: WILBERT ACEBO AUREO

Approved: VICTOR B. ASIO Date signed: _________ 2012 Adviser

Approved: MARLITO M. BANDE Date signed: _________ 2012 Chairman, Student Research Committee

Approved: FAUSTINO L. VILLAMAYOR Date signed: _________ 2012 Member, Student Research Committee

Approved: HUMBERTO R. MONTES Date signed: _________ 2012 Department Head

Approved: LINDA N. MARISCAL Date signed: _________ 2012 Registrar

Institute of Tropical Ecology and Environmental ManagementCollege of Forestry and Environmental Science

Visayas State UniversityVisca, Baybay City, Leyte

TRANSMITTAL

This Thesis manuscript, EVALUATION OF SOIL EROSION AND SEDIMENTATION RATES OF PANGASUGAN WATERSHED IN PANGASUGAN BAYBAY CITY, LEYTE, prepared and submitted by WILBERT ACEBO AUREO, in partial fulfilment of the requirements for graduation for the degree of BACHELOR of SCIENCE in ENVIRONMENTAL MANAGEMENT; ls hereby accepted.

VICTOR B. ASIOADVISER

_________, 2013 DATE

Accepted as partial fulfilment of the requirements for graduation for the dgree of BACHELOR of SCIENCE in ENVIRONMENTAL MANAGEMENT.

HUMBERTO R. MONTESDIRECTOR, ITEEM-CFES

_________, 2013 DATE

ACKNOWLEDGEMENT

TABLE OF CONTENTS

Evaluation of Soil Erosion and Sedimentation Rates of Pangasugan Watershed in Pangasugan Baybay City, Leyte

¹A Thesis manuscript presented in partial fulfillment of the requirements for graduation with the degree of Bachelor of Science in Environmental Management from the College of Forestry and Environmental Sciences Visayas State University, Baybay City, Leyte on ___________Contribution No._____. Prepared in the Institute of Tropical Ecology and Environmental Management under the guidance and supervision of Dr. Victor B. Asio.

Wilbert Acebo Aureo

CHAPTER 1

INTRODUCTION

Nature and Importance of the Study

Soil is the most basic of all resources, is nonrenewable. Once lost, it is difficult to replace

within the foreseeable future. New soil formation, development of a biologically productive and

economically fertile soil from parent rock, is a slow process measured only in a geological time

scale. It takes hundreds to thousands of years to develop the equivalent of a 5-cm layer of fertile

soil. The equivalent of 1 cm or more topsoil may be lost in a single rainstorm. Literally speaking,

the soil formed over hundreds to thousands of years can be blown or washed away in a single

climatic event (Lal 1990). On the other hand, soil erosion is the detachment of soil materials

including rock fragment by an agent to an area of deposition. It is important to study rate of soil

erosion because of its adverse effects on the environment. These effects include: nutrient loss,

soil diversity loss, burying of crops, deposition of sediments, occurrence of floods and water

pollution. The problem of water induced soil erosion in the tropics has gained on increased

public attention in recent years. The reasons for soil erosion in the tropic regions, besides the

removal of natural vegetation, especially the forest, are due to land use systems which are not

adapted to ecological conditions, e.g. monocropping of annual crops and overgrazing. The

increasing population in these climatically favorable tropical mountain regions reinforces the

pressure in limited, non renewable resources. The rate of soil erosion is affected by: rainfall,

discharge rate, streamflow, vegetation, drainage pattern, land use system and soil erodibility (soil

type). Erosion in watershed is one of the major devastative processes which affected both hilly

and lowland environments. Erosion in nature is not destructive but because of man’s interference

and mismanagement of the land, it has been magnified to the extent that it caused destruction of

low lying agricultural areas, watershed, marine environments and even lives and properties.

(Dudal 1988) reported that the current rate of agricultural land degradation worldwide by soil

erosion and other factors is leading to an irreversible loss in productivity on about 20 million ha

of fertile land a year.

Sedimentation embodies the process of detachment, transportation, and deposition of

sediment by the erosive and transport agents including raindrop impact and runoff over the soil

surface (ASCE, 1975). Like erosion, sedimentation has serious environmental and economic

implications. Sedimentation decreases the capacity of reservoirs and chokes irrigation canals and

tributaries. Also, sediments are a major source of pollution and eutrophication (the aging of lakes

caused by water enrichment). (Judson 1988) estimated the river-borne sediments carried into the

oceans increased from 10 billion tons a year.

Agriculturally speaking, both erosion and sedimentation affect soil productivity through

their respective on-site and off-site effects. Erosion reduces on-site productivity by decreasing

the rooting depth and depleting nutrient and water reserves. Sedimentation lessens productivity

through off-site effects such as decreasing the capacity of water reservoirs and silting of

irrigation canals. Soil erosion and sedimentation are severe in temperate and tropical, whenever

the land is used beyond its capability by crop and soil management systems that are ecologically

incompatible.

Pangasugan watershed is located at Brgy. Pangasugan, Baybay City, Leyte where the

climate is more or less rainy. Pangasugan is generally built up by andesitic and basaltic

pyroclastic rocks (referred to as Pangasugan formation) which are mostly of Quaternary and

Tertiary origin. This rock formation is characterized by weak consolidation, lithologic

discontinuities, abundance of rock outcrops, and shearing due to the occurrence of the Philippine

fault line approximately at the center of the mountain range. Minor earthquakes are relatively

frequent in the area Asio (2010). All these geological characteristics indicate that the area is

unstable, thus expectation on the rates of soil erosion and sedimentation is high. Also,

Pangasugan watershed comprises different land use systems and is very suitable on studies

related to soil erosion and sedimentation. Moreover, studies on soil erosion are very minimal in

the region where in fact, soil erosion is one vital factor on determining the environmental status

of a watershed. Hence, the study will be conducted to determine the rates of soil erosion and

sedimentation and the factors associated. In the Philippines, extreme soil erosion is widely

observed because of less data on soil erosion rate. Thus the study is vital especially for the

records of VSU.

Objectives of the Study

1. To determine the rates of soil erosion and sedimentation of the Pangasugan watershed.

2. To evaluate the factors affecting the rates of soil erosion and sedimentation of the

Pangasugan watershed.

3. To determine the amount of nutrients ( N, and P ) lost through soil erosion.

Scope and Limitation

The study will only focus on the determination and evaluation of soil erosion and

sedimentation rates and the factors associated on it for a period of three months. These factors

include: rainfall intensity, vegetation, slope or topography, streamflow, land use system and soil

erodibility (e.g. soil type). Also the study determines nutrient that was lost due to erosion

specifically Nitrogen and Phosphorus.

Time and Place of the Study

The study was conducted at the Pangasugan watershed of Brgy. Pangasugan, Baybay

City, Leyte, on November to February, 2013. Study sites that are choosen were shifting

cultivation kaingin), coconut monocropping and intact forest.

REVIEW OF RELATED LITERATURE

Soil Erosion

Soil erosion is a major environmental threat to the sustainability and productive capacity

of agriculture ( David et al. 1995). Soil erosion is not just a problem of modern times, although

in the past 50 years there has been more awareness of its consequence, more understanding of

the process involved and more knowledge of its cause-effect relationships than ever before. Soil

erosion began with the dawn of agriculture, when people began using the land for settled and

intensive agriculture (Lal 1990). According to some estimates, soil erosion and other degradative

processes have destroyed, over the millennia, as much arable land as is now cultivated (Kovda,

1977). Soil erosion results in a net loss of irreplaceable soil with constituents that are needed for

crop production such as nutrients and organic matter being washed away. The seriousness of soil

erosion in our watershed areas is attributed to some factors such as rainfall, slope, soil

characteristics, vegetation cover and system of cultivation practiced by farmer. The magnitude of

soil loss in cultivated sloping areas has reached to an alarming proportion.

Soil Erosion in the Philippines

Land degradation and soil erosion are among the most serious environmental paroblems

in the world. In the Philippines erosion and watershed degradation are also cited as one of the

major longterm environmental hazards (e.g.Saplaco1979,David 1984,Arocena-Francisco

1986,Porter and Ganapin 1988,USAID 1989,PCARRD 1991,Sajise etal1992). According to

Paningbatan (1989), soil loss rates were much higher than the acceptable tolerable loss of 3 t ha -1

year-1. Moreover, he found that erosion on bareplots (no vegetation) with slopes of 27 to 29%

ranged from 23 to 218 t ha-1 year-1. David and Collado (1967), estimated the rill and erosion rates

in Magat watershed (located in Isabela south of Cagayan) basin) to reach as high as 239 in

savannah, 264 in open grassland and 587 t ha-1 year-1 in kaingin areas.

In Leyte Island, visual observation would indicate the severity of erosion problem in

hillylands due to exposure of subsurface layers, gravelly top soils and even the bedrock itself. In

terms of growth for eroded areas with vegetation, performance of plants in the area is very

improvished which is a big sign of infertility.

Factors of Soil Erosion

Rainfall

Rainfall is an active agent that directly affects soil erosion .Raindrop

impact cause the destruction of soil aggregates and clogging of the soil

pores promoting runoff that carries along the detached sediments. According

to Paningbatan (1989), the Philippines generally experiences highly erosive

rainstorms with an average annual rainfall amount of 4.2 meters. When the

rate of rainfall exceeds the rate of infiltration, it causes surface runoff

(Beasley 1972). .  As rain falls from the sky it has tremendous force and as it

impacts the soil it can break away small portions of soil and make it erosion

likely.  This is why rainfall is an important soil erosion factor, but the amount

of rain, type of rain, and the distribution of rain are what really need to be

looked at. Water and soil splash follows a single raindrop impact. Rain may

move soil directly: this is known as 'rainsplash erosion' (or just 'splash

erosion'). Spash is only effective if the rain falls with sufficient intensity. If it

does, then as the raindrops hit bare soil, their kinetic energy is able to

detach and move soil particles a short distance. Because soil particles can

only be moved a few centimetres at most by this process, its effects are

solely on-site. Although considerable quantities of soil may be moved by

rainsplash, it is all merely redistributed back over the surface of the soil (on

steep slopes, however, there will be a modest net down slope movement of

splashed soil). Thus a more descriptive term might be 'rainsplash

redistribution'. Because rainsplash requires high rainfall intensities, it is most

effective under convective rainstorms in the world’s equatorial regions.

Slope and Elevation

Slope is another factor to consider which either represses or triggers soil erosion. In

sloping areas which is about 10M ha (Ly Tung and Balinda, 1993), soil erodibility is high, hence

highly susceptible to erosion. According to Schachtschavel et al (1982) as cited by Reigning

(1992)), overland flow and soil loss increases with increasing length of slope, however, this

influence is less pronounced compared to the steepness of the slope. Slope length is defined as

the distance from the point of overland flow to the point where either the slope gradient

decreases enough that the deposition begins or run off enters a well-defined channel that maybe

part of a drainage network or a constructed channel (Weschmeier and Smith, 1978). Slope is

critical factors in determining soil erosion.  As you know there are fields with all kinds of

slopes.  Flat fields with 1-2 percent slopes may not be very prone to erosion, but fields with

slopes of 10-15 percent slopes will likely be very prone to erosion. .  Long fields with a constant

slope of 2 percent may erode severely, because as the water runs off the field it builds

momentum and the faster the water runs the more energy it has for transporting soil. 

Vegetation and Land use system

Vegetation provides protection to the soil by absorbing the kinetic energy of raindrops

giving little chance for water to exert destructive impact to the ground (Lal 1988). Soil cover

provided by natural vegetation or agricultural crops reduces soil loss mainly because leaves

intercept raindrops and thus reduce kinetic energy. This reduces the splash effect of raindrops

significantly and prevents disintegration of soil aggregates (Scwertmann, 1981). According to

Weschmeier and Smith (1987), a complete grass sod is the most effective way to cover the soil

and control erosion the effectiveness of any crop, management system or protective cover also

depends on how much protection is available at various periods during the year, relative to the

amount of erosive rainfall that falls during these periods. In this respect, crops which provide a

food, protective cover for a major portion of the year (for example, alfalfa or winter cover crops)

can reduce erosion much more than can crops which leave the soil bare for a longer period of

time (e.g. row crops) and particularly during periods of high erosive rainfall (spring and

summer). However, most of the erosion on annual row crop land can be reduced by leaving a

residue cover greater than 30% after harvest and over the winter months, or by inter-seeding a

forage crop (e.g. red clover). . Land use practice also influences detachability of soil particles

(Reining 1992). Thus removal of natural vegetation coupled with massive tillage operations in

sloping lands would loosen the soil, enhancing soil removal during rainstorm. Soil erosion

potential is affected by tillage operations, depending on the depth, direction and timing of

plowing, the type of tillage equipment and the number of passes. Generally, the less the

disturbance of vegetation or residue cover at or near the surface, the more effective the tillage

practice in reducing erosion. Land use system in tropics, especially in the mountain areas are

characterized by small scale farming and mixed cropping.

Soil Erodability

There are thousands of different soil types around the world and each of them has

properties, which make them unique.  One of their properties is their soil erodability.  Some soils

are just much more susceptible to eroding than others.  I am currently working with a farmer who

has a field with only 2% slope, but this field is eroding at a rapid rate.  As I investigated the soil I

learned that the soil was primarily silt.  Silty type soils tend to be the most erosive.  In much of

the world there is a layer of silt, which was deposited by wind.  This wind blown silt, which is

referred to as loess, is probably the most erosive soil.  Soils that have a relatively high content of

clay tend to be the least erosive soils.

As you all know soils have a mixture of sand silt and clay in them, and in many soils the ratio is

very similar.  However, even with soils with similar ratios of sand, silt and clay may have

drastically different soil erodability properties.  Can you think of what may also change the soil's

erodability?  The two, which first come to my mind, is soil structure, and rock content.  Soil with

good soil structure will allow more water infiltration and thus reducing runoff water and erosion. 

This is also true of rock soils.  They also tend to have greater water infiltration rates.  The

numerical value to describe a soil erodability ranges from 0.2 – 0.4 in my area. 

Sedimentaion and Streamflow

All rivers carry sediments, due to surface erosion from watersheds and bank erosion

along the river ( Yang 1996 ). Excessive input of fine sediment (sand, silt, clay) generally is

considered to be the most prevalent form of pollution currently affecting streams and rivers in

the United States. Because of the erosive force of flowing water, the presence of fine sediment in

streams is an entirely natural phenomenon. In fact, a dynamic balance in streams normally exists

between the particle size and amount of sediment transported by a stream, and the discharge and

slope of the stream. A variety of human activities can lead to abnormally high rates of sediment

input, upsetting this balance and resulting in increased concentrations of sediment in the water

column (i.e., increased turbidity) and increased deposition of sediment on the stream bottom.

Both of these factors can have serious adverse effects on the biota and ecology of streams.

The major anthropogenic sources of sediment to streams are agriculture (especially row-crop

cultivation in floodplains and livestock grazing in riparian zones), forestry (with logging roads

contributing far more sediment than other practices, including clear-cutting), mining, and urban

development. Of these, agriculture is by far the most significant source of anthro-pogenically

derived sediment. It has been estimated that agriculture contributes about 50% of all sediment

pollution in the United States (Kohler et al. 1997).

Nutrient Loss and Soil erosion

Soil erosion is one of several processes contributing to on-site nutrient depletion. Nutrient

depletion can also be a contributing cause of soil erosion because, when nutrients are limiting,

there is lower production of above- and below-ground biomass which protects the soil against

erosion. This is less frequently recognized than the fact that erosion causes nutrient depletion.

The quantity of nutrient loss by soil erosion is the product of soil loss and the nutrient content of

sediment, but may also be predicted from soil loss and topsoil nutrient content. However, erosion

selectively removes topsoil. The nutrient-rich sediment is further enriched by the selective

deposition of faster-settling particles during transport. Thus, prediction of nutrient depletion must

take this enrichment process into account ( Hashim, et al. 1998 ).

MATERIALS AND METHODS

1. Selection of Study Sites

Potential study sites in different land use systems were prospected based on

topographic map, land use map and geologic map. On the actual field survey three (3)

study sites were selected. The sites chosen were: shifting cultivation (kaingin), coconut

monocropping and an intact forest.

2. Field Measurements and Sampling

Soil erosion

Three (3) erosion plots were established in each study site. In addition, a canal

that will serve as catchment was also been established in each plot for the

collection of eroded soil. Monitoring of soil erosion rate will be done once per

week for three (3) months. The eroded soil collected was brought to DASS

laboratory for analysis. In addition, three erosion bars was also installed in each

plot to measure soil erosion rate. Reading was done once per month.

Sedimentation

Stream water samples were collected four times from each sampling site, one (1)

liter bottles were used. Three (3) replications per sampling period per site were

observed. Collection was done at the middle, and side portions of the stream.

Sediment load was determined by letting the water evaporates using a hot plate

and the sediment was weighed.

Streamflow

For steamflow analysis a standard requirements of locating gauging sites was

followed. Three sites along the main stream channel in upper, middle and

downstream portions of the river were chosen. This includes the very slow

flowing section, moderately fast flowing section and a section having a faster

flow. In every gauging site measuring of the stream widths and so with the

distance among which the float (ping pong ball) shall travel was done. The

distance must be uniform for all three sites. At least three float-time trials was

observed in every site. Cross-sectional depth of the river under study was

determined. Measurements were done every 20 centimeter section across the

river. Stream discharge was computed using as follows;

Q – (A x V) .85

where: Q - is the stream discharge in cu.m. per second

A – average cross-sectional depth times stream width

(grand mean values)

V- grand mean velocity in meters per

second. 0.85- velocity correction factor

Soil erodibility

Soil erodibility was determined following John et al. (2003).

Land use system

Land use system was determined on the actual conduct of the study.

Meteorological Data

Data on rainfall (mm) and rainfall intensity throughout the duration of the study

will be obtained from the records of PAGASA station, VSU, Visca, Baybay,

Leyte (macroclimate) and by using an improvised rain gauge (microclimate).

Laboratory Analysis

Soil samples were brought to DASS laboratory for pH, Organic Matter, N and P

determination.

pH (Potentiometric Method)

Soil pH was analysed potentiometrically using a 1:2.5 soil and water ratio (ISRIC

1995). A 20 g sieved soil was weighed and placed into a properly labeled plastic

cup. It was added with 50 mL of distilled water and is stirred thoroughly so that a

suspension will be formed. The solution was stirred every 15 minutes for 1 hour

before reading in a precalibrated pH-meter (Mothrem).

Organic Matter (Modified Walkley-Black Method)

Soil Organic Matter was analyzed using a modified Walkley – Black method

(PCCAR 1980). Exactly 0.5 gram of sieved soil (0.425 mm sieve) was weighed

and placed into a 500 mL Erlenmeyer flask. Using a volumetric pipette, the soil

was oxidized by adding 10 mL of 1 N K2Cr2O7 and then swirled gently to

dispense the solution. At the fume hood, 10 mL of concentrated H2SO4 was added

rapidly and swirl the flask for 1 minute. The mixture was allowed to react at the

fume hood for one hour before adding 200 mL of distilled water. Thereafter, a 4

drops of O-Phenanthroline indicator was added before the final titration with 0.5

N FeSO4. Endpoint of the titration was reached, a clearly visible maroon

coloration was observed. Percent soil organic matter was computed using the

formula:

% SOM=(1− SB )0.069 1

w

Where: SOM – Soil Organic Matter

S – Volume of Ferrous Sulfate used in the sample (mL)

B – Volume of Ferrous Sulfate used in Blank (mL)

W – Weight of the Soil Sample.

Total Nitrogen (Kjeldahl Method)

Total Nitrogen was determined using kjeldahl method (USDA, 2004).

Digestion

A gram of soil was sieved using a 0.425 mm sieve and place into a 100 mL

digestion flask. A gram of selenium reagent mixture was added to the soil and

mix thoroughly by swirling. Under the fume hood, a 6 mL of concentrated H2SO4

was added to the mixture until the mixture condenses about one-third of the way

up to the neck of the flask. The flask was rotated at 20 minutes interval to

facilitate the digestion of the sample. The digestion was stoped when frothing or

charring ceases leaving a white precipitate. The flask was removed from the

digester and allowed to cool. Ii. Ii.

Distillation

30 mL distilled water was slowly added to the digest. The flask was swirled. The

digest was transferred into a Buchi distilling flask and was add 50 mL of 40%

NaOH. The flask was holded at about 45 sec. Then the flask was attached to the

distillation set-up. For the receiver of the distillate, a 125 mL Erlenmeyer flask

with 25 mL of 2% H3BO3 and three drops of mixed indicator were put just

beneath the flask. The distillate was titrated with 0.05 N H2SO4 until the color of

the solution mixture changes from green to pink. A blank solution was prepares

and the same determination process was done.

Total Nitrogen was computed using the formula:

% N=(a−b)× N ×0.014W

×100

Where: N – Nirmality of H2SO4

a – mL

of H2SO4 in

soil Sample

b – mL

of H2SO4 in

the blank

W – weight of the soil 0.014 –

meq. wt. of Nitrogen

Available Phosphorus (Olsen method)

Available Phosphorus (ppm) was determined following the Olsen method. Soils

that have pH above 7.0 was extracted using NaHCO3 at pH 8.5 as extracting

solution. A 2-5 g sieved soil sample was weighed and place in a 50 mL

Erlenmeyer flask. A 25 mL extracting solution NaHCO3 was added and mixed

using a reciprocating shaker for 5 minutes within a minimum of 180 oscillations

per minute. After shaking, the mixture was filtered using Whatmann #42 filter

paper (optional). The filtrate was collected using a plastic receiver. Using a

volumetric pipette, a 2 mL Aliquot was added with reagent C (mixture of

ammonium molybdate, potassium antimony titrate, and ascorbic acid) and mix

using a vortex mixer. 2 mL of the working solution was added with reagent C and

shake. Also a blank sample was also prepared. Percent transmittance was read

using a B-L Spectronic 20. Convert the value obtained into Optical density (OD).

The ppm P in the solution and in the soil was calculated using the formula:

ppm P∈the solution=ODS× K

Where: ODS – Optical Density of the sample

K – Slope of the standard curve for P

K= ppm P standard% Absorbance

ppm P∈Soil=ppm P∈solution× 252.5

×dillution

Where: 25 – volume of extracting solution (mL) : 2.5– weight of soil (g)

3. Data Analysis

Analysis of Variance (ANOVA) and linear regression were analyzed after the

collection of the data.

RESULTS AND DISCUSSION

Site Location

Figure 1. Map showing the three sites.

VSU

Pangasugan River

Site1 - Kaingin

Site2- Coconut monocropping

Intact Forest

LITERATURE CITED

Asio V.B. 2010, The Physical Environment of Mt. Pangasugan, Leyte, Philippines, SOIL

and ENVIRONMENT: soil and its relation to agriculture, environment, global

warming, and human health. Available @:

http://soil-environment.blogspot.com/2010/03/physical-environment-of-mt-

pangasugan.html

Flavio S. Anselmetti et al. 2007. Quantification of soil erosion rates related to Mayan

deforestation., also available at:

http://www.ask.com/web?

qsrc=32

7 & o=102140 & l=dir & q=soil+eosion+and+sedimentation+rates & oo=102140

Hashim, G. M. et al. 1998. Soil erosion at multiple scales: principles and methods for

assessing causes and impacts. pp. 207-221

John R, H.P. Blume and V.B. Asio 2003. Student Guide for soil description,

Classification and Evaluation. University of Halley, Germany.

Kovda, V.A,Dregne, H.E.; Henning, D.; Flohn, H 1977: Status of desertification in the

hot arid regions. Climate aridity index map. Experimental world scheme

of aridity and drought probability. At a scale of 1:25,000,000, United

Nations Conference on Desertification. Nairobi (Kenya), 29 Aug 1977.

Kohler S. et al. 1997. Effects of Sedimentation on Stream Communities. Center for

Aquatic Ecology also available at: http://www.inhs.illinois.edu/inhsreports/may-

jun97/streams.html

Lal R.: Soil Erosion in the Tropics-principles and management, McGraw- Hill Inc. R.R.

Donnelley and Sons Company: 1990

Miller R.H. and Keeney D.R.In: Methods of Soil Analysis. Part 2. Chemical and

Microbiological properties. 2nd ed. Eds. A.L. Page, x.

Nelson D.W and L.E. Sommers. 1982. Total Carbon, and Organic Matter. Pp. 539-579

Olli S. 1994. Off-Site Costs of Soil Erosion and Watershed Degradationin the

Philippines: Sectoral Impacts and Tentative Results DISCUSSION

PAPER SERIES NO. 94-18

Paningbatan, E.P., A.R. Maglinao, L.A.Calanog and G.M. Huelgas. 1992.

Managementof sloping lands for sustainable agriculture in the Philippines.

In: Technical Reporton the Management of Sloping Lands for Sustainable

Agriculture in Asia,Phase 1, 1988-1991 (IBSRAM/ASIALAND).

Network Document No. 2

Pasa A.E. 1997. Effects of Rainfall and watershed characteristics on the water yield of

Molawin watershed. Unpublished MSc Thesis, UPLB. College, Laguna.

Pimentel D. et al. 1995. Environmental and Economic Costs of Soil Erosion and

Conservation Benefits. Science New Series Vol. 265 No.250

Reining L.–Weikersheim; Margraf,,.Erosion in Andean Hillside Farming;

characterization and reduction of soil erosion by water in small scale cassava

cropping systems 1992.

Scwertmann, U. 1981. Die Vorausschatzung des Bodenabtrags in Bayern (Verfahren

Wischmeier and Smith). Bayer. St. Ministerium f. Ernahung, Landwirtschaft und

Forsten Munchen.

United States Agency for International Development (USAID), Manila, Philippines.

1989.Sustainable Natural Resources Assessment - Philippines. Prepared

by:Dames & Moore International, Louis Berger International, Inc. and Institute

for Development Anthropology.

Wischmeier, N.H., D.D. Smith 1978, Predicting rainfall erosion looses-a guide to

conservation planning. U.S. Department of Agriculture, Agriculture Handbook

No. 537, Washington D.C.

Yang, C.T. (1 996). Sediment Transport Theory and Practice, The McGraw-Hill

Companies, Inc.,New York (reprint by Krieger Publishing Company, Malabar,

Florida, 2003).

Sample Initial Final Consumed Duplicate

Initial

Duplicate

Final

Duplicate

Consumed

Grand

average

Organic

matter

S1P1 0 10.1 10.1 10.1 20.6 10.5 10.3

S1P2 10.7 19.5 8.8 19.5 29 9.5 9.15

S1P3 0 9.1 9.1 9.1 18,2 9.1 9.1

S2P1 10.6 19.1 8.5 19.1 28.4 9.3 8.9

S2P2 0 5.6 5.6 5.6 10.7 5.1 5.35

S2P3 18.2 28.1 9.9 28.1 38.5 10.4 10.15

S3P1 20.6 28.8 8.2 0 8.4 8.4 8.3

S3P2 29.0 37.1 8.1 0 9.4 9.4 8.75

S3P3 11.2 20.2 9.0 20.2 28.3 8.1 8.55

Blank 0 22.7 22.7 2.1 24.5 22.4 22.55

Table 1. Data on Organic Matter.

Sample Wt. container Wt. container +

sediment

Sediment

(grams)

Average

sediment (mg)

S1B 93.42 93.77 0.35 35

S1S 99.01 99.08 0.07 7

S1S 103.85 103.96 0.11 11

S2B 92.58 92.59 0.01 1

S2S 87.96 87.99 0.03 3

S2S 89.93 89.96 0.03 3

S3B 95.02 95.13 0.11 11

S3S 89.53 89.56 0.03 3

S3S 94.18 94.19 0.01 1

Table 2. Data on sedimentation rate ( December 28, 2012 ).

Sample Wt. container Wt. container +

sediment

Sediment

(grams)

Average

sediment (mg)

S1B 93.42 93.47 0.05 5

S1S 99.01 99.05 0.04 4

S1S 103.85 103.89 0.04 4

S2B 92.58 92.60 0.02 2

S2S 87.96 87.99 0.03 3

S2S 89.93 89.97 0.04 4

S3B 95.02 95.05 0.03 3

S3S 89.53 89.59 0.06 6

S3S 94.18 94.19 0.01 1

Table 3. Data on sedimentation rate (January 4, 2013)

Sample Wt. container Wt. container +

sediment

Sediment

(grams)

Average

sediment (mg)

S1B 94.52 94.55 0.03 3

S1S 95.19 95.21 0.02 2

S1S 96.91 96.92 0.01 1

S2B 94.58 94.59 0.01 1

S2S 95.29 95.31 0.02 2

S2S 92.61 92.63 0.02 2

S3B 95.02 95.04 0.02 2

S3S 102.60 102.61 0.01 1

S3S 92.07 92.07 0 0

Table 4. Data on sedimentation rate (January 11, 2013)

Sample Wt. container Wt. container +

sediment

Sediment

(grams)

Average

sediment (mg)

S1B 94.52 94.58 0.06 3

S1S 95.19 95.23 0.04 2

S1S 96.91 96.96 0.05 1

S2B 94.58 94.60 0.02 1

S2S 95.29 95.31 0.02 2

S2S 92.61 92.63 0.02 2

S3B 95.02 95.04 0.02 2

S3S 102.60 102.61 0.01 1

S3S 92.07 92.09 0.02 2

Table 5. Data on sedimentation rate (January 18, 2013).

Site/Location Width

stream

(meter)

Sectional

depth (m)

Distance

(m)

Time

(Second)

Velocity

(d/t)

Stream

flow

(cu.m/sec)

Very slow

flowing

Sub total 13.28 4.85 17.55 226.77

Sub mean 4.43 0.4409 5.85 75.59 0.0773

Moderately

flowing

Sub total 9.88 4.425 17.55 51.79

Sub mean 3.29 0.4425 5.85 17.26 0.3389

Fast flowing

Sub total 15.42 2.71 17.55 28.57

Sub mean 5.14 0.2085 5.85 9.52 0.6145

Grand total 38.58 11.985 52.65 307.13

Grand mean 4.29 0.3640 5.85 34.12 0.3437 0.4562

Table6. Data on stremflow (January 28, 2013).

Site/Location Width

stream

(meter)

Sectional

depth (m)

Distance

(m)

Time

(Second)

Velocity

(d/t)

Stream

flow

(cu.m/sec)

Very slow

flowing

Sub total 12.52 4.16 17.55 168.24

Sub mean 4.17 0.38 5.85 56.08 0.104

Moderately

flowing

Sub total 7.18 3.96 17.55 43.93

Sub mean 2.39 0.396 5.85 14.64 0.400

Fast flowing

Sub total 13.60 2.04 17.55 27.05

Sub mean 4.53 0.16 5.85 9.02 0.649

Grand total 33.3 10.16 52.65 239.22

Grand mean 3.70 0.312 5.85 26,58 0.38 0.3729

Table 7. Data on streamflow analysis ( Feb. 09, 2013)

Site Location Elevation (masl) Average Slope (%)

S1P1 N 10º 45.578’

E 124º 47.981’

71 85

S1P2 N 10º 45.577’

E 124º47.953’

71 77.5

S1P3 N 10º 45.580’

E 124.º47.955’

69 80

S2P1 N 10º45.591’

E 124º47.964’

58 55

S2P2 N 10º45.588’

E 124º47.966’

62 62.5

S2P3 N 10º45.586’

E 124º47.962’

65 75

S3P1 N 10º45.793’

E124º48.269’

70 80

S3P2 N 10º45.790’

E 124º48.272’

72 86

S3P3 N 10º45.789

E 124º48.274’

75 95

Table 8. Data on site location, slope and elevation.

Date Amount of Rainfall (mm)

Nov. 19-23, 2012 50.8

Nov. 24-30, 2012 12.5

Dec. 1-7, 2013 53.0

Dec. 8-14, 2013 12.7

Dec. 15-21, 2013 155. 5

Dec. 22-28, 2013 124.5

Dec. 29-Jan. 4 115.5

Jan. 5-11, 2013 53.5

Jan. 12-18, 2013 63.4

Jan.19-25, 2013 25.8

Jan. 26-Feb.1 .100.2

Feb. 2-8,2013 26.9

Feb.9-15,2013 91.2

Table 9. Data on rainfall in weekly basis from PAGASA VSU station.

Site 1

Plot 1 Plot 2 Plot 3

R1 R2 R3 R1 R2 R3 R1 R2 R3

38 32 39.7 32.6 34 39.8 27.4 30.2 33.4

35.8 29.7 35.4 32.9 34.7 39.1 25.4 31.8 34.5

37.3 29.5 33.9 33.3 31.4 37.9 28.5 32.3 35

37.6 30 35.3 34.4 33.3 34.5 25.2 33.2 35.2

36.5 30 34.4 36.6 33.2 33.9 26.7 31.4 36.2

Site 2

Plot 1 Plot 2 Plot 3

R1 R2 R3 R1 R2 R3 R1 R2 R3

39.4 38.4 37.9 41.3 38.4 37.9 37.4 33.8 40.4

37.8 38.8 39.8 44.5 38.8 39.8 37 35.3 36.1

37.2 40 41.3 44.9 40 41.3 37.5 39./9 35.5

35.2 40.9 40.3 44.4 40.9 40.3 37.2 38.3 36.5

35.3 41.4 40.4 45.3 41.4 40.4 37.6 34.8 37.2

Site 3

Plot 1 Plot 2 Plot 3

R1 R2 R3 R1 RF2 R3 R1 R2 R3

36.1 41.2 42.1 33.1 30.9 37.2 37.9 36 37.2

36.4 39.9 43.5 29.6 28 38 33 35.3 37

32.5 41.3 41.7 31.9 32.3 32.4 30.3 34.6 37.2

35 41.2 34.9 33.4 31.9 30.4 26.2 36.5 34.3

30.7 35.2 35 34.3 31.6 29.4 22.5 36 33

Table 11. Data on Sedimentation rate. (November 19, 2012)

Site 1

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 R2 R3 R1 R2 R3

1 3.3 2.9 2.4 2.0 2.2 2.8 2.1 3.9 3.3

2 3.1 4.0 3.5 1.9 1.8 2.7 2.3 1.4 2.0

3 1.9 3.9 3.7 3.5 3.2 2.6 2.1 2.6 3.6

4 2.0 3.3 3.3 2.8 3.4 2.8 3.1 2.7 2.1

5 2.0 4.1 2.4 1.9 2.7 1.7 2.5 3.3 3.7

Averag

e

2.46 3.64 3.06 2.42 2.66 2.52 2.42 2.78 2.94

Site 2

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 R2 R3 R1 R2 R3

1 1.2 2.7 1.8 2.1 1.2 1.0 2.4 1.0 0.4

2 1.6 2.0 2.0 2.3 1.0 0.7 2.5 1.3 1.3

3 2.0 1.2 2.0 1.9 1.1 1.5 1.3 0.3 4.3

4 1.1 1.0 2.0 0.8 2.0 2.6 2.4 1.6 0.8

5 1.5 1.7 3.0 2.0 1.4 1.4 1.6 3.4 1.4

Averag 1.48 1.72 2.16 1.52 1.34 1.44 2.04 1.52 1.64

e

Site 3

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 RF2 R3 R1 R2 R3

1 1.4 1.5 2.4 1.3 0.7 1.0 0.3 0.9 1.2

2 2.3 1.3 1.1 1.6 2.8 1.2 1.8 3.1 0.9

3 0.7 1.1 1.2 1.4 2.0 1.0 2.7 1.2 1.7

4 0.9 2.7 0.4 2.0 0.2 1.1 1.6 0.8 1.9

5 1.9 1.4 0.9 1.5 1.0 2.4 1.4 1.1 1.2

Averag

e

1.44 1.60 1.20 1.56 1.34 1.34 1.56 1.42 1.38

Table 12. Data on soil erosion rate (cm). First Reading

Site 1

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 R2 R3 R1 R2 R3

1 2.6 3.7 0.5 1.5 2.6 1.7 2.4 2.7 2.1

2 2.0 0.7 1.3 3.1 1.2 0.8 1.9 0.8 3.2

3 1.8 2.5 1.8 1.2 1.2 3.3 0.5 1.9 1.4

4 1.1 2.8 1.1 1.9 1.9 1.9 1.6 2.4 1.3

5 3.9 1.7 3.1 2.2 1.6 1.9 3.2 1.9 1.5

Averag

e

2.28 2.28 1.56 1.98 1.70 1.92 1.92 1.94 1.90

Site 2

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 R2 R3 R1 R2 R3

1 1.6 1.5 1.9 1.9 1.8 1.2 2.0 0.8 1.9

2 1.2 1.4 0.4 0.9 1.9 1.5 3.7 1.5 1.5

3 2.2 0.5 1.7 1.1 0.7 1.4 6.6 2.1 1.4

4 2.6 1.7 2.2 2.1 1.4 2.3 3.5 0.9 2.5

5 0.4 1.5 2.3 1.5 0.8 3.1 4.4 1.4 1.3

Averag

e

1.60 1.32 1.50 1.50 1.32 1.90 4.04 1.34 1.72

Site 3

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 RF2 R3 R1 R2 R3

1 1.7 0.9 1.4 1.6 2.8 2.1 2.0 1.2 1.2

2 0.7 2.4 1.6 2.1 3.1 1.7 1.8 1.4 1.5

3 2.6 2.9 1.7 1.4 1.4 1.8 1.3 2.8 0.7

4 1.4 0.8 1.8 1.4 2.7 1.3 1.5 1.4 2.6

5 1.2 2.2 1.5 3.0 1.2 1.8 1.9 1.3 2.2

Averag 1.52 1.84 1.60 1.98 2.24 1.74 1.70 1.72 1.64

e

Table 13. Data on soil erosion rate (cm). Second Reading.

Site 1

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 R2 R3 R1 R2 R3

1 1.4 2.1 1.9 1.3 1.6 2.3 1.2 1.3 1.0

2 1.4 1.5 1.4 1.8 0.8 1.8 1.8 2.7 1.5

3 2.4 1.6 3.3 0.6 1.4 1.9 1.7 1.2 1.5

4 1.9 1.2 1.8 2.1 1.2 2.4 0.9 2.1 1.8

5 1.8 0.5 1.1 2.9 1.4 1.8 1.9 1.7 2.1

Averag

e

1.78 1.38 1.90 1.74 1.28 2.04 1.50 1.80 1.58

Site 2

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 R2 R3 R1 R2 R3

1 1.8 0.8 1.3 2.1 1.0 1.5 1.4 0.6 1.7

2 2.2 2.5 1.3 2.0 0.8 1.4 1.7 1.2 0.7

3 1.5 3.9 1.6 0.7 2.4 1.6 0.9 2.3 2.3

4 0.6 2.6 1.6 0.9 0.8 0.7 2.1 1.8 1.0

5 2.3 1.0 2.0 2.8 1.1 2.7 1.3 1.3 2.0

Averag

e

1.68 2.16 1.56 1.70 1.22 1.58 1.48 1.44 1.54

Site 3

Plot 1 Plot 2 Plot 3

Erosion

Bars

R1 R2 R3 R1 RF2 R3 R1 R2 R3

1 2.6 0.8 1.3 0.9 2.1 3.1 1.3 1.2 1.5

2 1.7 1.2 2.6 1.5 1.9 0.7 0.6 0.7 1.2

3 0.5 1.2 1.2 1.5 1.0 1.7 1.3 1.2 1.3

4 2.2 1.1 0.7 0.4 1.5 0.9 2.0 0.9 1.0

5 1.3 0.6 0.7 0.5 1.3 2.6 0.8 0.8 0.6

Averag

e

1.66 0.98 1.30 0.96 1.56 1.80 1.20 0.96 1.12

Table 14. Data on soil erosion rate (cm). (Final reading).