J. Basic. Appl. Sci. Res., 2(8)8218-8229, 2012

© 2012, TextRoad Publication

ISSN 2090-4304 Journal of Basic and Applied

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*Corresponding Author: Pitojo Tri Juwono, Department of Water Resources, Faculty of Engineering, University of Brawijaya, Malang, East Java of Indonesia. Email: pitojo_tj@ub.ac.id; pidiaa@yahoo.com

Evaluation of Flow Capacity and the Pattern of Water Requirement in Irrigation Area of Lereh, Jayapura Regency of Indonesia

Pitojo Tri Juwono1*, Dwi Priyantoro1, Nimbrot Rumaropen2

1Department of Water Resources, Faculty of Engineering, University of Brawijaya,

Malang, East Java of Indonesia 2Master Program of Water Resources, Faculty of Engineering, University of Brawijaya,

Malang, East Java of Indonesia

ABSTRACT This paper intended to study the suitable pattern of water requirement in irrigation area of Lereh. In addition this study wanted to evaluate the flow capacity of bearer channel based on the water demand due to the selected cropping pattern. The methodology consisted of analysing dependable discharge of 80% and irrigation water balance due to the some alternative of irrigation water supply and cropping pattern. The methods which were used in this study included Stagnant Constant Head (SCH), System of Rice Intensification (SRI), and combination of the both system. Alternative of cropping patterns were rice-rice-second crop, rice-rice/second crop-second crop, and rice-second crop-second crop. Design of water distribution for every cropping season due to the Relative Second-crop Factor (FPR) and K factor was based on the balance analysis of irrigation water requirement. Result showed that selected cropping pattern was rice-rice and second crop-second crop with enough water supply criteria of 0.12 < FPR < 0.23, but field water demand due to the SRI method with water stagnant of 2 cm, water distribution interval on the vegetative phase was 5-8 days and the generative phase was 7-10 days, and it was hoped to have been enough. The channel capacity was designed to be able to flow the maximum discharge of 2,300 l/s and the minimum discharge of 300 l/s due to the available velocity control between 0.6 and 1.5 m/s in order not to be occured sedimentation and erosion in the irrigation channel. The results could be used as the consideration on distribution optimal water distribution and it could be known the channel capacity of bearer channel in flowing irrigation water due to the cropping demand Keywords: irrigation, water distribution, cropping pattern, SCH, SRI, flow capacity

INTRODUCTION Planning of water resources is not an easy job mainly when the case is as national wide [1][2]. It becomes complex when an area is unstable or some events are unpredictably [3]. The main objective of water resources management is to make balance of the demand and supply of water resource for a specific area taking into account various dimensions like time, space, politics, economy, environment, and other aspects. Regional decision making is considered to a variety of technical aspects which is needed for being decided [4]. Water resources development in Indonesia was targeted to supply some kinds of water needs. The kinds of water needs include for irrigation,industry, hydro electrical power, recreation, and daily human needs. Indonesia is as a agricultural country. Therefore the important aspect of water resources development is used for irrigation. One of the Indonesian government efforts for implementating food suffering especially in outside of Java island was carried out in Papua Province. Indonesian government has opened the potential area of Lereh irrigation area that is located in Yapsi District of Jayapura Regency. The irrigation area of Lereh used the water source from Nawa river through the Lereh Weir as water capturing with flowing the water by gravitation system. The system was planned for supplying the agricultural area of 2,119.36 ha. The planned cropping included rice and second crop. There were some efforts had to be carried out for obtaining the maximal agricultural production like the usage of well rice varietas, optimal distribution of irrigation water, regular vertilizing, and wiping out the plant disease accurately. Irrigation scheme was generally designed by using design flood as the maximum discharge which could be flowed through the intake gate of weir. This maximum discharge could only be reached if the water supply in river was sufficient. Whereas in dry season, water supply in river was decreased so that would decrease the flowed discharge through intake gate. If the channel which is designed by high design flood being flowed with low actual discharge so the flow velocity will decrease. If the actual flow velocity is under the arrangements of minimum velocity, the water is not able flowing to the farest structure and if the irrigation water contents sediment, it will occur sedimentation. Based on the reason as above, it was nacessary to make a special study about the pattern of optimal water use in order to function the irrigation channel well and it also important to evaluate the flowing capacity of existing bearer channel. It was hoped the maximal and increasing agricultural production due to this special study.

Juwono et al., 2012

MATERIALS AND METHODS The irrigation area of Lereh is located in Yapsi District, Jayapura Regency, Papua Province of Indonesia. Map of location is as in Figure 1. This area is fall between south latitude of di 2o49’23,53” and east longitude 140o06’59.46” .

Figure 1 Map of location Lereh irrigation area is as a potential agricultural area with well soil fertilizing. The water source comes from Nawa river with Lereh weir as the water capturing. Lereh weir included two intakes such as the left one for supplying the irrigation area of 1414.76 ha and the right one for supplying of 704.60 ha. Data collecting in this study used surey approach. The data was collected indirectly from the related institution as secondary data. This secondary data included data of hydrology, climate, topography, geology, and agriculture. The steps of analysing data were as follow:

1. To analyze the design flood using Log Pearson Type III and Unit Synthetic Hydrograph of Nakayasu for controlling the main structure.

2. To analyze water supply using the method of dependable discharge due to the ouput data of Mock method.

3. To analyze irrigation water requirement based on the some alternative of cropping pattern and crop type using Design Criteria Method of General Working, Stagnant Constant Head Method (SCH), and System of Rice Intensification Method (SRI).

4. To analyze water balance between water supply and demand in the irrigation area of Lereh. 5. To design the pattern of water requirement using the method of Relative Second crop Factor (FPR) and

K for every cropping season by dividing the Lereh irrigation area into some blocks. 6. To analyze the cropping rotation time based on the pattern of water supply. 7. To evaluate the channel design based on the water demand during the preparation of area, maintenance

of crop, and cropping time of second crop. Water balance Water balance in an irrigation area is nacessary to be made for dectecting the condition of irrigation water demand and dependable discharge in the intake. Analysis of water balance is based on the irrigation water demand of used cropping pattern compared with dependable discharge. If the river discharge overflows, the irrigation water demand will be fulfilled and if the river discharge does not overflow, it indicates the lack of discharge. Evapotranspiration Evapotranspiration is the process union of evaporation and transpiration, This study used the method of Penman Modification for analyzing the potencial evaporation (ETO) with the formula as follow [5]

ETo = c ETo* ......................................................................................... (1) ETo* = w (0,75 Rs – Rn1) + (1-w) f (U) (ea-ed) ...................................... (2)

Note:

Lereh

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J. Basic. Appl. Sci. Res., 2(8)8218-8229, 2012

w = factor that related to the area temperature and elevation; Rs = radiation of short wave; Rγ = radiation of short wave in the limitation of atmosphere outside ( ≈ angot number); Rn = net radiation of long wave; Rn1 = f(t) f(ed) f(n/N ); f(t) = temperature function; f(ed) = vapour pressure function; ed = ed* RH; RH = relative humidity; f(n/N) = sunshine function; f(U) = wind velocity function in the height of 2 m; (ea – ed) = the difference between satiated and really vapour pressure; and c = corecction factor Analysis of dependable and effective rainfall Dependable rainfall is as the rainfall along year with failure risk has been calculated. This study used the method of basic month. Effective rainfall is rainfall dropping in an area and it can be used by the crop for growing. The effective rainfall can be used to supply water demand in order to decrease the discharge which was needed from intake. The formula of effective rainfall for rice and second crop is as follow [6]:

Reff for rice = 70% x R80 ........................................................ (3) Reff for second crop = R50 .................................................................... (4)

Note: R80 = dependable rainfall with the probability of 80% R50 = dependable rainfall with the probability of 50% Cropping arrangement The factors which influence water demand in wet rice field included crop water demand, percolation, water demand for preparation work, water demand for cultivation, water demand for water layer change, and efficiency of irrigation. Some important things related to cropping arrangement are as follow:

1. Cropping pattern Cropping pattern is intended to use irrigation water supply efficiently so that the crop can well grow. Two important things related to cropping pattern are the limitation of water supply during dry season and every tertiary block is nacessary to receive enough water due to the demand. There were four things being arranged in design of cropping pattern such as the cropping schedule, the cropping location, the arrangement of crop type, and the arrangement of cropping number area.

2. Cropping schedule The arrangement of cropping schedule is intended to use the water supply in river for irrigation effectively due to the demand of every area.

3. The form and type of cropping pattern There are two times cropping schedule in one year such as in rainy season (October to March) and dry season (April to September). The restriction of time is used to determine the begnning schedule of rice cropping in rainy season as well as the other type of crop. The alternative of cropping pattern that is generally used is rice-rice-second crop, rice-rice-second crop-second crop, or rice-second crop-second crop.

Irrigation water requirement There are some methods for analysis irrigation water requirement as follow:

1. Design Criteria Method of Public General Work (PU) This method is as standard method which is used in Indonesia for design of irrigation. The formula of this method is as follow [7]: - Water demand in wet rice field:

NFR = LP + ETc + P – Reff + WLR - Water demand in intake for rice:

IRrice = Eff

NFR

- Water demand in intake for second crop:

IRsecond crop = Eff

ffReETc

Note: LP = water demand for area preperation and cultivation; Etc = crop water demand; P = percolation; WLR = water demand for water layer change; Reff – effective rainfall; Eff = efficiency of irrigation

2. Stagnant Constant Head Method (SCH) SCH method is the method of irrigation water distribution by irrigating the wet rice field with the certain height for soil preparation as well as the crop maintenance. Water demand in wet rice field for the phase of area preparation as well as crop maintenance is based on the Relative Second crop Area (LPR). LPR is the comparation between base area to the second crop which is based on the water demand to the other crop. Analysis of crop water demand used Relative Second crop Factor (FPR).

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FPR is the minimum allowed water distribution which the second crop can grow without considering water loss in channel as well as in wet rice field. The formula of FPR due to the agricultural soil type is as follow:

FPR = LPR

Q

Note: Q = flow discharge in river and LPR = number area of relative second crop If FPR has been designed, water demand in intake is formulated as follow: Q = FPR x LPR

Note: FPR = factor of designed relative second crop and LPR = number area of relative second crop in the submerged wet rice field.

3. System of Rice Intensification (SRI) method SRI method principally is as the method of intermittent water distribution. At the SRI plantation, the condition of water supply in area is arranged so that the area is dry enough but it remain fulfills the crop water demand. Distribution of irrigation water is carried out by giving submerged height of 2 cm during 5-10 days depends on the growth phase. Irrigation water demand with SRI method is formulated as follow [8]:

Q1 = T

AxH x 10.000

Q2 = L1

1x86.400

Q1

Note: Q1 = daily water demand in the field; Q2 = daily water demand in intake; H = submerged height; A = number area of wet rice field; T = interval of water distribution; L = water loss in the filed and channel

The pattern of water requirement Based on the distribution method, water distribution for rice crop is divided as follow: continuous flow, continous submergence, and intermittent. Water distribution can be based on the comparison between irrigation water supply and demand or the water distribution by K factor which is formulated as follow:

Factor of K = QdQi

Note: Qi = supply discharge in intake; Qd = demand discharge Water distribution due to block system is a water distribution method regularly and concentrated in the area of technical irrigation and based on the area by area which the irrigation area is divided into some blocks.

Capacity of bearer channel Bearer channel in the irrigation scheme is designed to be able to flow water discharge as follow [7]:

Q = e

ANFRc

Note: Q = design discharge; c = decreasing coefficient because of the block system; NFR = fresh water demand in wet rice field; A = number area of irrigated wet rice field; e = total efficiency of irrigation.

Bearer channel in irrigation scheme included as follow: 1. Soil channel without lining

Parameter that has to be determined in hydraulic design of channel is the comparison between water depth and tight base width of long slope. The channel flow is assumed as steady flow by applying Strickler formula with the assumption that longitudinal section of channel as trapezoid shape as in Figure 2 below [9].

Figure 2 channel longitudinal section

J. Basic. Appl. Sci. Res., 2(8)8218-8229, 2012

The general equation of discharge which flows in trapezoid opened channel is as follow: Q = v A

v = 1/22/3 IRk

R = PA

A = (b + m h) h P = 1mh2b 2 b = n h

Note: Q = channel discharge; v = flow velocity; A = longitudinal section; R = hydraulic radius; P = wet periphery; b = base width; h = water depth; I = energy slope (= channel slope); k = coefficient of Strickler; m = talud slope (1 vertical : m horizontal) Research of Lim and Kim [10] presented that minimum velocity which is allowed to decrease sedimentation and the growth of wild grass in the channel without lining is 0.45 m/s for small channel and 0.60 m/s for bog channel.

2. Channel with lining

The giving lining in irrigation channel is intended to prevent water loss due to the seepage, scouring and erosion, and act violently and arbitrarilly of water vegetation; to decrease maintenance cost, to give loose for the more bend and little of soil releasing. The allowed minimum velocity in lining channel is minimum velocity which does not cause sedimentation and wild grass growing and the minimum velocity is 0.45 m/s for small channel and 0.60 m/s for big channel [10].

RESULTS AND DISCUSSION

Design flood Flood hydrograph of a river is generally used for analysing design flood. There was not Automatic Water Level Recorder (AWLR) in the location of study, so that was used the synthetic unit hydrograph of Nakayasu. Analysis result of design flood is presented as in Table 1. Table 1 Recapitulation of design flood

No Periode (year)

Q (m3/s)

H (m)

Elevation of water level

1 2 3 4 5 6 7 8

1.01 2 5

10 20 25 50 100

35.84 189.51 276.50 329.79 370.69 392.64 436.61 478.27

0.69 1.80 2.32 2,61 2,82 2,93 3.14 3.34

69.74 70.95 71.47 71.76 71.97 72.08 72.29 72.49

Dependable discharge Transformation from rainfall to discharge in this study used Mock method. Dependable discharge of 80% was based on basic month method. The result is presented as in Figure 3.

Figure 3 Illustration result of dependable discharge of 80% and rainfall

Month - period

d i c h a r g e

(m3

/s)

r a i n f a l l

(mm)

Rainfall Q80

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Juwono et al., 2012

Evapotranspiration Analysis of potential evaporation in this study used the method of Penman Modification. Climate data was collected from Meteorology and Climatology Station of Sentani which is located at the height of 99 m above sea water level with south latitude of di 2o30’ and east longitude 140o28’48”. Climate data used in this study was in the year of 2000 until 2010. Analysis result of potential evaporation is presented as in Table 2.

Table 2 Potential evaporation for Sentani Station using Penman Modification Method Item Unit Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec Etp mm/day 4.33 4.08 4.13 4.35 3.87 3.59 3.66 4.00 4.46 4.55 4.25 4.06

Effective rainfall Based on the analysis of average monthly rainfall during 11 years, the coefficient of average effective rainfall was 0.3 until 0.6. Therefore if it was remained due to the design standard of 0.7, it will give the high risk of failure.

Percolation Soil type in location of study is dominated by loam-sandy loam, so the percolation rate when soil preparation was estimated as 10 mm/day and after soil preparation (during the crop maintenance) was estimated as 3 mm/day. Water demand for area preparation Area preparation was carried out together with cultivation during 30-45 days before rice cropping time as shown in Table 2.

Table 2 Water demand for area preparation Water layer changing Water layer changing was carried out for one time when the vegetation age was 20-30 days after vegetation moving. The design depth of water layer was 50 mm during 30 days. The calculation of water layer changing was as follow: WLR =

days30mm50 = 1,667 mm/days

Efficiency of irrigation The average of irrigation efficiency in the location of study with new channel condition included ± 90% of primary channel, ± 90% of secondary channel, and ± 65% of tertiary channel. Therefore, the total efficiency was 65%.

Irrigation water requirement Analysis of irrigation water requirement in this using Design Criteria Method of Public Work Department (PU), Stagnant Constant Head (SCH) Method, System of Rice Intensification (SRI) Method, and the

Month Eo (mm/day)

P (mm/day)

M (mm/day)

K= M.(T/S)

IR (mm/day)

Jan I II

4.76 3.00 7.76 1.40 10.31 4.76 3.00 7.76 1.40 10.31

Feb I II

4.49 3.00 7.49 1.35 10.12 4.49 3.00 7.49 1.35 10.12

Mar I II

4.54 3.00 7.54 1.36 10.15 4.54 3.00 7.54 1.36 10.15

Apr I II

4.79 10.00 14.79 2.66 15.90 4.79 10.00 14.79 2.66 15.90

May I II

4.25 10.00 14.25 2.57 15.44 4.25 10.00 7.25 1.31 9.95

June I II

3.95 3.00 6.95 1.25 9.74 3.95 3.00 6.95 1.25 9.74

July I II

4.03 3.00 7.03 1.27 9.79 4.03 3.00 7.03 1.27 9.79

Aug I II

4.40 3.00 7.40 1.33 10.05 4.40 0.00 4.40 1.33 8.04

Sep I II

4.91 0.00 4.91 0.88 8.36 4.91 0.00 4.91 0.88 8.36

Oct I II

5.00 0.00 5.00 0.90 8.43 5.00 0.00 5.00 0.90 8.43

Nov I II

4.68 10.00 14.68 2.64 15.80 4.68 10.00 14.68 2.64 15.80

Dec I II

4.47 10.00 14.47 2.60 15.62 4.47 10.00 14.47 2.60 15.62

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combination of SRI, SCH. The alternatives of cropping pattern were rice-rice-second crop as alternative-1; rice-rice & second crop-second crop as alternative-2; and rice-second crop-second crop as alternative-3. The calculation of irrigation water requirement for Lereh irrigation area was as follow: 1. Design Criteria of Public Work Department (PU):

- Water demand in wet rice field NFR = LP + ETc + P – Reff + WLR

- Water demand in intake for rice

IRrice = Eff

NFR

- Water demand in intake for second crop

IRsecond crop = Eff

ffReETc

Result of irrigation water demand for the three alternatives of cropping pattern was presented as in Figure 4.

Figure 4 Water balance curve due to Public Work Method (MU) of Q80% 2. Stagnant Constant Head (SCH) Method Analysis of irrigation water demand by using Stagnant Constant Head (SCH) was based on the criteria of Relative second crop factor (FPR). Table 3 presented the value of FPR by using the method of Public General Work (PU) that was compared to water supply based on the Mock Method Table 3 Analysis of LPR-FPR by using Q80%

No Item Unit CP-1 CP-2 CP-3 1 Number area of rice ha 2,119.4 2,119.4 0

Number area of second crop ha 0 0 2,119.4 2 Water supply average for cultiation l/s/ha 2,56 1,84 0,00

Water supply average for crop maintenance l/s/ha 1,03 0,73 0,30 3 Q dependable (80%) l/s 1,409 856 164 4 LPR for cultivation ha.pol 9 6,1

LPR for crop maintenance ha.pol 3,4 2,4 1,0 5 FPR l/s/ha.pol 0,2 0,2 0,1

Note: LPR = Relative number area of second crop, FPR = Relative second crop factor, CP = cropping pattern In addition, the value of FPR was also determined based on the soil type of Latosol as shown in Table 4 below. Table 4 The value of FPR in study location based on the soil type

Item FPR (l/s/ha.pol) Less water Enough water Available water

Water distribution < 0.12 0.12-0.23 >0.23 CP-1 0.20 CP-2 0.20 CP-3 0.15 Turning Nacessary possible no

Source: General Public Work Department Level 1 of East Java (1977) One of the irrigation water demand using SCH method based on the FPR criteria was presented as in Figure 5.

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

I II I II I II I II I II I II I II I II I II I II I II I II

Nop Des Jan Feb Mar Apr Mei Jun Jul Agust Sep Okt

Q (m

3 /dt

)

Bulan

GRAFIK HUBUNGAN ANTARA KEBUTUHAN AIR DAN KETERSEDIAAN AIR Q80%

Q Andalan 80%

Q keb Alt. 1

Q keb. A lt. 2

Q keb Alt. 3

Relation curve between water demand and water supply of Q80%

Q m3/s

Q80% Alternative-1 Alternative-2 Alternative-3

month

Juwono et al., 2012

Figure 5 Water balance curve using SCH method for alternative-2 of rice-rice & second crop-second crop with Q80%

3. System of Rice Intensification (SRI) Method [11] The pattern of irrigation water distribution in every approaching location is different and it is depended on the agro-ecology and irrigation water supply. In this study, there was designed the water distribution when crop maintenance on vegetative phase of cropping pattern-1 and it was 2 cm for 8 days and generative phase of 10 days, but for vegetative phase of cropping pattern-2 was 2 cm for 5 days and generative phase of 7 days. One of the irrigation water demand using SRI method was presented as in Figure 6.

4. Combination of SCH and SRI Method The other alternative of irrigation water distribution was carried out by combining between SRI and SCH method. This combination is intended to find the optimal water demand based on the available dependable discharge. The SRI method was applied in the right side of Lereh Block and the first left side of Lereh Block, but SCH method was applied in the second left side of Lereh Block. One of the irrigation water demand using the combination of SCH and SRI method was presented as in Figure 7.

0

500

1000

1500

2000

2500

3000

3500

I II I II I II I II I II I II I II I II I II I II I II I IINop Des Jan Feb Mar Apr Mei Jun Jul Agust Sep OktMT 3 MT 1

MT 2MT 3

Q (l

t/dt

)

Periode

Grafik Hubungan Antara Kebutuhan Air Blok Golongan 1 - 3 dengan Q 80%Alternatif 2 : Padi - Padi+Palawija - Palawija

Lereh Kanan

Lereh Kiri 1

Lereh Kiri 2

Q 80%

0

500

1000

1500

2000

2500

1 4 7 10 13 16 19 22 25 28 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100 103 106 109 112 115 118 121 124 127 130

II I II I II I II I II I II

Mar AprMei Jun

JulAgust

Pengolahan tanah Awal Vegetatif anakanPembungaan Pengisian bulir masak - susu

Pematangan

DEBI

T (m

3/dt

))

MT II

GRAFIK PEMBERIAN AIR METODE SRI/ INTERMITTENT DI. LEREH MT. II (ALTERNATIF 2)

Lereh Kanan

Lereh Kiri 1

Lereh Kiri 2

Q 80%

Figure 6 Water balance curve using SRI method for alternative-2 of rice-rice & second crop-second crop with Q80%

0

500

1000

1500

2000

2500

1 4 7 10 13 16 19 22 25 28 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100 103 106 109 112 115 118 121 124 127 130

II I II I II I II I II I II

Mar AprMei Jun

JulAgust

Pengolahan tanah AwalVegetatif anakan

PembungaanPengisian bulir masak - susu

Pematangan

DEBI

T (m

3/dt

))

MT II

GRAFIK PEMBERIAN AIR KOMBINASI METODE SRI - SCH DI. LEREH MT. II (ALTERNATIF 2)

Lereh Kanan

Lereh Ki ri 1

Lereh Ki ri 2

Q 80%

Figure 7 Water balance curve using the combination of SCH and SRI method for alternative-2 of rice-rice & second crop-second crop with Q80%

Period

Relation Curve between water demand block 1 to 3 with Q80% Alternative-2: rice-rice+second crop-second crop

Q (m3/s)

Lereh kanan Lereh kiri-1 Lereh kiri-2 Q-80%

Relation Curve between water demand block 1 to 3 with Q80% Alternative-2: rice-rice+second crop-second crop

Lereh kanan Lereh kiri-1 Lereh kiri-2 Q-80%

Q (m3/s)

J. Basic. Appl. Sci. Res., 2(8)8218-8229, 2012

The recapitulation of water balance based on the methods of PU, SCH, SRI, and the combination of SCH and SRI by using K factor for determining Turn Criteria (KG) as follow: 1. KG > 0,8 : Continuous 2. 0,6 < KG ≤ 0,8 : Turn of Blok C 3. 0,4 < KG ≤ 0,6 : Turn of Blok B and C 4. KG ≤ 0,4 : Turn of Blok A, B, and C

The recapitulation result of water balance was presented as in Table 5 and the recapitulation of turn level in every cropping season for the four methods was presented as in Table 6.

I II I II I II I II I II I II I II I II I II I II I II I II

Water supply

Qdependable 80% m3/s 0,20 0,72 0,48 1,32 1,11 0,97 1,03 2,41 2,09 2,33 1,02 1,25 1,38 0,86 0,70 0,72 0,42 0,36 0,33 0,19 0,33 0,20 0,39 0,16

Water demand

1. PU Method

a. Alternative-1 0,34 1,39 2,63 3,40 2,84 2,19 2,19 2,19 2,19 1,51 1,86 2,10 2,87 2,43 1,92 1,92 1,92 1,92 1,53 1,17 0,75 0,75 0,75 0,75

b. Alternative-2 0,34 1,39 2,63 3,40 2,84 2,19 2,19 2,19 2,19 1,48 1,27 0,78 1,18 1,04 1,12 1,12 1,12 0,82 0,73 0,56 0,75 0,75 0,75 0,75

c. Alternative-3 0,34 1,39 2,63 3,40 2,84 2,19 2,19 2,19 2,19 1,46 0,79 0,20 0,38 0,47 0,47 0,47 0,47 0,27 0,33 0,48 0,75 0,75 0,75 0,75

Factor of K

a. Alternative-1 0,6 0,5 0,2 0,4 0,4 0,4 0,5 1,1 1,0 1,5 0,5 0,6 0,5 0,4 0,4 0,4 0,2 0,2 0,2 0,2 0,4 0,3 0,5 0,2

Note gilir gilir gilir gilir gilir gilir gilir continucontinucontinu gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir

b. Alternative-2 0,6 0,5 0,2 0,4 0,4 0,4 0,5 1,1 1,0 1,6 0,8 1,6 1,2 0,8 0,6 0,6 0,4 0,4 0,5 0,3 0,4 0,3 0,5 0,2

Note gilir gilir gilir gilir gilir gilir gilir continucontinucontinucontinucontinucontinucontinu gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir

c. Alternative-3 0,6 0,5 0,2 0,4 0,4 0,4 0,5 1,1 1,0 1,6 1,3 6,3 3,6 1,8 1,5 1,5 0,9 1,4 1,0 0,4 0,4 0,3 0,5 0,2

Note gilir gilir gilir gilir gilir gilir gilir continucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinu gilir gilir gilir gilir gilir

2. SCH Method

a. Alternative-1 0,28 1,52 2,65 3,18 2,40 1,48 1,48 1,48 1,48 1,06 1,94 2,65 3,18 1,48 1,48 1,48 1,48 1,48 1,10 0,85 0,32 0,32 0,32 0,32

b. Alternative-2 0,28 1,52 2,65 3,18 2,40 1,48 1,48 1,48 1,48 1,02 1,10 0,78 1,08 0,77 0,77 0,77 0,77 0,57 0,44 0,32 0,32 0,32 0,32 0,32

c. Alternative-3 0,28 1,52 2,65 3,18 2,40 1,48 1,48 1,48 1,48 0,99 0,54 0,14 0,27 0,42 0,42 0,42 0,42 0,28 0,26 0,32 0,32 0,32 0,32 0,32

Factor of K

a. Alternative-1 0,7 0,5 0,2 0,4 0,5 0,7 0,7 1,6 1,4 2,2 0,5 0,5 0,4 0,6 0,5 0,5 0,3 0,2 0,3 0,2 1,0 0,6 1,2 0,5

Note gilir gilir gilir gilir gilir gilir gilir continucontinucontinu gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir continu gilir continu gilir

b. Alternative-2 0,7 0,5 0,2 0,4 0,5 0,7 0,7 1,6 1,4 2,3 0,9 1,6 1,3 1,1 0,9 0,9 0,5 0,6 0,8 0,6 1,0 0,6 1,2 0,5

Note gilir gilir gilir gilir gilir gilir gilir continucontinucontinucontinucontinucontinucontinucontinucontinu gilir gilir gilir gilir continu gilir continu gilir

c. Alternative-3 0,7 0,5 0,2 0,4 0,5 0,7 0,7 1,6 1,4 2,4 1,9 8,9 5,1 2,0 1,7 1,7 1,0 1,3 1,3 0,6 1,0 0,6 1,2 0,5

Note gilir gilir gilir gilir gilir gilir gilir continucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinu gilir continu gilir continu gilir

3. SRI Method

a. Alternative-1 0,31 1,44 1,54 1,89 0,88 0,82 0,76 0,70 0,70 0,58 1,58 1,72 2,23 1,40 1,27 1,15 1,00 0,67 0,46 0,30 0,30 0,30 0,30 0,30

b. Alternative-2 0,31 1,44 1,54 1,89 0,88 0,82 0,76 0,70 0,70 0,51 0,79 0,69 0,95 0,67 0,69 0,64 0,58 0,45 0,36 0,25 0,30 0,30 0,30 0,30

c. Alternative-3 0,31 1,44 1,54 1,89 0,88 0,82 0,76 0,70 0,70 0,47 0,25 0,10 0,19 0,30 0,30 0,30 0,30 0,30 0,30 0,30 0,30 0,30 0,30 0,30

Factor of K

a. Alternative-1 0,6 0,5 0,3 0,7 1,3 1,2 1,3 3,4 3,0 4,0 0,6 0,7 0,6 0,6 0,6 0,6 0,4 0,5 0,7 0,6 1,1 0,7 1,3 0,6

Note gilir gilir gilir gilir continucontinucontinucontinucontinucontinu gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir continu gilir continu gilir

b. Alternative-2 0,6 0,5 0,3 0,7 1,3 1,2 1,3 3,4 3,0 4,5 1,3 1,8 1,5 1,3 1,0 1,1 0,7 0,8 0,9 0,7 1,1 0,7 1,3 0,6

Note gilir gilir gilir gilir continucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinu gilir continucontinu gilir continu gilir continu gilir

c. Alternative-3 0,6 0,5 0,3 0,7 1,3 1,2 1,3 3,4 3,0 5,0 4,0 12,7 7,3 2,9 2,4 2,4 1,4 1,2 1,1 0,6 1,1 0,7 1,3 0,6

Note gilir gilir gilir gilir continucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinu gilir continu gilir continu gilir

4. SCH-SRI Method'

a. Alternative-1 0,43 1,66 1,78 2,02 1,10 1,04 0,98 0,98 0,98 0,98 2,09 1,95 2,35 1,43 1,30 1,18 1,18 0,84 0,64 0,30 0,30 0,30 0,30 0,30

b. Alternative-2 0,43 1,66 1,78 2,02 1,10 1,04 0,98 0,98 0,98 0,84 1,16 0,78 1,00 0,69 0,70 0,65 0,65 0,52 0,43 0,25 0,30 0,30 0,30 0,30

c. Alternative-3 0,43 1,66 1,78 2,02 1,10 1,04 0,98 0,98 0,98 0,75 0,54 0,10 0,19 0,30 0,30 0,30 0,30 0,30 0,30 0,30 0,30 0,30 0,30 0,30

Factor of K

a. Alternative-1 0,5 0,4 0,3 0,7 1,0 0,9 1,0 2,5 2,1 2,4 0,5 0,6 0,6 0,6 0,5 0,6 0,4 0,4 0,5 0,6 1,1 0,7 1,3 0,6

Note gilir gilir gilir gilir continucontinucontinucontinucontinucontinu gilir gilir gilir gilir gilir gilir gilir gilir gilir gilir continu gilir continu gilir

b. Alternative-2 0,5 0,4 0,3 0,7 1,0 0,9 1,0 2,5 2,1 2,8 0,9 1,6 1,4 1,2 1,0 1,1 0,7 0,7 0,8 0,7 1,1 0,7 1,3 0,6

Note gilir gilir gilir gilir continucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinu gilir gilir gilir gilir continu gilir continu gilir

c. Alternative-3 0,5 0,4 0,3 0,7 1,0 0,9 1,0 2,5 2,1 3,1 1,9 12,7 7,3 2,9 2,4 2,4 1,4 1,2 1,1 0,6 1,1 0,7 1,3 0,6

Note gilir gilir gilir gilir continucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinucontinu gilir continu gilir continu gilir

Item UnitNov Dec Oct

m3/s

Jan Feb Mar Apr May Jun

m3/s

m3/s

m3/s

Jul Aug Sep

Juwono et al., 2012

Table 6 Recapitulation of Turn Level

Schedule of turn in Lereh Irrigation Area Schedule of turn was made based on the evaluation result of water distribution from each method. The aim of turn schedule is to regulate the rotation time in determined each block. Based on the water supply, it was made the pattern of turn operation with the alternative of maximum discharge was 2,00 l/s; the average discharge was 1,150 l/s; and the minimum discharge was 300 l/s as in Table 7 below. Table 7 Operation pattern of turn discharge

Evaluation of channel design Evaluation of channel design was carried out by considering the flow velocity during the phase of area preparation, rice crop maintenance, and second crop demand. Design velocity was fitted to the soil type where the channel was build. Bearer channel in Lereh Irrigation area was as masonry channel so that according to the Criteria of Irrigation Design [3], it was said that the minimum velocity which did not cause sedimentation and wild grass growing in channel was 0.45 m/s for small channel and 0.6 m/s for big channel. To evaluate the design of bearer channel, permitted range of velocity was 0.6 m/s until 1.5 m/s. The channel was evaluated based onthe demand discharge during the phase of area preparation, rice crop maintenance, and second crop demand. The evaluation result showed that some channels were safe to the problem of sedimentation and erosion but in some section there was possible to occur sedimentation because the flow velocity was under the permitted range. The recapitulation on design evaluation of bearer channel was presented as in Table 8 below. Table 8 Evaluation result of bearer channel design in Lereh irrigation area

MT 1 Q 80% 7 x 7 x 7 x 7 x 7 x 7 x 4 x 4 x 4 x 5 x 5 x 5 x

MT 2 Q 80% 8 x 4 x 1 x 8 x 3 x 0 x 7 x 1 x 0 x 7 x 3 x 0 x

MT 3 Q 80% 4 x 4 x 4 x 4 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x

Total Q 80% 19 x 15 x 12 x 19 x 13 x 10 x 14 x 8 x 7 x 15 x 11 x 8 x

PU MethodCropping ppattern

Dependable discharge

Alt. 1 Alt. 2 Alt. 3

SCH_SRI Method

Alt. 1 Alt. 2 Alt. 1 Alt. 2 Alt. 3 Alt. 1 Alt. 2 Alt. 3

SCH Method SRI Method

Alt. 3

Debit water depth Discharge water depth discharge Water depth

(Block) (lt/s) (ha) (lt/s) (m) (lt/s) (m) (lt/s) (m)

(A) Lereh Kanan Q min 705 1268,28 0,05 14 493,22 0,02 5 105,69 0,00 0

(B) Lereh Kiri 1 300,00 648 1165,97 0,05 12 453,43 0,02 5 97,16 0,00 0

(C) Lereh Kiri 2 767 1380,60 0,05 15 536,90 0,02 6 115,05 0,00 0

(A) Lereh Kanan Q average 705 1268,28 0,05 4 493,22 0,02 1 105,69 0,00 0

(B) Lereh Kiri 1 1150,00 648 1165,97 0,05 3 453,43 0,02 1 97,16 0,00 0

(C) Lereh Kiri 2 767 1380,60 0,05 4 536,90 0,02 2 115,05 0,00 0

(A) Lereh Kanan Q max 705 1268,28 0,05 2 493,22 0,02 1 105,69 0,00 0

(B) Lereh Kiri 1 2300,00 648 1165,97 0,05 2 453,43 0,02 1 97,16 0,00 0

(C) Lereh Kiri 2 767 1380,60 0,05 2 536,90 0,02 1 115,05 0,00 0

Water supply

Supply day

Name of DI Irrigation Area

Irrigation water demand of riceWater demand for second crop

Preparation Area Maintenance

supply (day)

supply day

BLA.5 - BMLA.5 BLA.0 - BLA. 6

BLA.7 - BMLA.7 BLA.6 - BLA. 7

BLI.4 - BLI.8

BLI.2 - BMLI.2.1

BLI.9 - BMLI.9.1 13 sec BLI.0 - BLI.3

BLI.11 - BMLI.11.2 BLI.9 - BMLI.11.2

Block

BLA.0 - BLA.8 BLA.5 - BLA. 7

all of sectionBLI.0 - BLI.4

sedimentation section safe section

Phase of area preparation

sedimentation section

BLI.0 - BLI.11 BLI.3 - BLI.9

Lereh-right

Lereh-left-1

Lereh-left-2

2 sec

6 sec

2 sec

8 sec

4 sec

8 sec

9 sec 6 sec

Phase of second crop

sedimentation section

safe section

all of section -

all of section -

-all of section

the same section

2 sec

Phase of maintenance

10 sec

J. Basic. Appl. Sci. Res., 2(8)8218-8229, 2012

CONCLUSION The conclusion of this study was as follow:

1. Design of cropping pattern If there was shown from the function of water supply through irrigation system based on the rice crop, it was hoped the reaching of minimum crop intensity was 180% (alternative I and II). But if there was based on the rice crop and second crop, the reaching of minimum crop intensity (government allowance) was 225% (alternative I, II, and III). Design of cropping pattern in Lereh irrigation area was presented as in Table 9. Table 9 Design of cropping pattern in Lereh irrigation area

2. The pattern of water distribution and division - The pattern of water distribution

Irrigation water distribution for SCH method due to the FPR criteria for enough water was: 0,12 < FPR < 0,23; but for SRI method by using 2 cm of water depth and the interval of water distribution was 5 to 8 days for vegetative phase and 7 to 10 days for generative phase.

- The pattern of irrigation water division Based on the operation pattern of turn discharge, the preparation area phase needed the maximum discharge of 2,300 l/s so that was not occur a long time in the turn level. The maintenance phase and second crop needed the average discharge of 1,150 l/s until the minimum discharge of 300 l/s.

3. Design evaluation of bearer channel Based on the evaluation of bearer channel design, it was shown that during the phase of area preparation, the velocity in channel was not more than 1.5 m/s and not less than 0.6 m/s, and the sedimentation was only occured in the farest section of channel. Sedimentation was occured in almost the whole section during the phase of maintenance and second crop. For the farest tertiary block, it was nacessary to be added the travel time of irrigation water until to the block of tertiary block. Whereas the addition of turn time based on the travel time to each block was presented as in Table 9 below. Table 9 Recapitulation of travel time

REFERENCES

1. Limantara, Lily Montarcih. 2010. Possible Climate Change Effect on Water Irrigation at Golek, Malang, Indonesia. Journal of Economics Engineering, No. 3: 15-17

2. Hoesein, Abdul Azis and Limantara, Lily Montarcih. 2010. Linear Programming Model for Optimization of Water Irrigation Area at Jatimlerek of East Java. International Journal of Academic Research, No. 2(6): 55-57

3. INWRDAM. 2001. Decision Support System in the Field of Water Resources Planning and Management. Published on line in http://www.nic.gov.jo/inwrdam/dss.htm1, March 12, 2001.

4. Pavoni, B; A. Voinov and N. Zhavora. 2001. Basin (Watershed) Approach As A Methodological Basis for Regional Decision Making And Management in the EX USSR. Published on line in http://helios.unive.it/%7Eintas/gaboart.htm1, March 12, 2001

base of rice crop base of rice crop and second cropI rice 100% - rice 100% - second crop 100% 200% 300%II rice 100% - rice 40% and second crop 60% - second crop 100% 140% 300%III rice 100% - second crop 100% - second crop 100% 100% 300%

Crop intensity reachingAlternative Cropping pattern

(hour) (day) (hour) (day) (hour) (day)

Lereh-right 17,72 1,12 22,88 1,43 36,26 2,27Lereh-left-1 14,88 0,93 19,67 1,23 33,18 2,07Lereh-left-2 28,30 1,77 37,98 2,37 72,34 4,52

travel time travel timePhase of maintenance

travel timeBlock

Phase of area preparation Phase of second crop

Juwono et al., 2012

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10. Lim, Y. C and Kim, D. S. 1981. Hydraulic Design Practice of Canal Structures. Korea Rural Environmental Development Institute. Seoul.

11. Sofiyuddin, Hanhan A.; Triyono, Joko; dan Subari. 2010. Pemberian air irigasi pada budidaya padi SRI di musim hujan dan kemarau. Jurnal Teknik Hidraulik 1 (2) : 123-136.

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