9. Estimated project cost of soft components
1.2 Drought water discharge Calculation method
Drought water discharge is set up considering results calculated according to the following 2 means.
(1) Measurement result of discharge at the site
(2) Estimation using discharge data at the similar rivers Result of calculation
(1) Measurement result of discharge at planned head work site
Discharge measured at planned head work site on 1st February, 2012 was approximately 3.8m3/s.
(2) Estimation using discharge data at the similar river
i) Similarity of natural condition
Generally, main rivers in Bhutan have its source in the alpine-tundra area with its elevation more than 3,000m, represented by the Himalayas. In other hand, as for Taklai River maximum elevation of catchment area is around 2,600m and catchment area does not have the alpine-tundra area. Considering these condition, similarity of natural condition of the catchment area to that of Taklai River is judged by criteria shown as below.
a) Elevation of catchment area is less than 3,000m b) Catchment area does not have alpine-tundra area.
c) Catchment area is close to or nearby that of Taklai River.
ii) River discharge data at the similar rivers
Rivers conforming to criteria mentioned above are Mau River, Bhur River and Sarpang River. At these rivers, minimum water discharge is measured once a year during January to March. Analysis results of drought water discharge of each river are shown in the table below. Unit discharge of each river is almost same.
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Drought water discharge (m3/s)
River 744.63 8.1644 (0.0110)
River 81.00 0.8157
(0.0101)
River 135.25 1.4033 (0.0104)
0.0105 0.0113 0.0130 0.0110 0.0108
iii) Estimation of drought water discharge at planned head work site
Estimated drought water discharge at the site multiplying average of unit discharge shown in the table above and catchment area at the site is shown in the table below.
Drought water discharge (m3/s) (Unit discharge (m3/s/km2))
River 86.24 0.9055 0.9745 1.1211 0.9486 0.9314
(3) Consideration
Head work is designed with water intake capacity more than 2.24m3/s, planned maximum irrigation requirement.
A discharge of Taklai River measured on 1st February, 2012 at the planned head work site was approximately 3.8m3/s. In other hand, 1.12m3/s is calculated as drought water discharge with 1year occurrence probability using discharge data at the similar rivers. Therefore although head work is designed with enough capacity, it is inferred that planned maximum irrigation requirement 2.24m3/s will not be able to be supplied from Taklai River all the year.
In practice, after paddling for spring cropping (January) soil of paddy land will be in the satiation condition and water requirement in dept will be decrease. So that it is supposed that in March, dry season, it will not be necessary to supply maximum amount of water to paddy land. However when double cropping starts after construction of Taklai irrigation system, the following treatment will be required.
- If discharge of Taklai River is supposed to be less than maximum irrigation requirement, beneficiary area should be divided into some area and water will be supplied in turn, not supply for whole the area in one time.
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1
Appendix-6.4 A study for the result of Taklai River discharge measurement Since Taklai river on which head works are planned to be constructed has no record of its discharge, design flood discharge at the head works construction point is calculated using rational formula.
Although it is just for reference, river discharge at the head works construction point has been observed through this study to grasp the specification of river discharge. Contents of observation is shown in the table below.
1. Observed item River depth using water gauge installed inside of Taklai river.
2. Calculation method of river discharge
By H(river depth)-Q(river discharge) formula created using the result of topographic survey
3. Duration From January 29th to July 7th (from dry season to beginning of rainy season) 4. Frequency 1 time/day (AM 8:00)
The relation between daily rainfall observed at Bhur observation station and observed river discharge Q1 is shown in the figure-1. These two kinds of data do not have high interrelation.
The relation between daily rainfall observed at Bhur observation station and river discharge Q2 calculated by rational formula is shown in the figure-2. It is difficult to find out interrelation between Q1 and Q2.
The flood reaching time is estimated as 2 hours but available rainfall data is daily amount and river discharge is only one time in a day. The reason of gap between Q1 and Q2 is that these rainfall and river discharge data is not enough to grasp meteorological and hydrological condition within flood reaching time.
In Bhutan, some observation stations have telemeter system and send observed data each hour automatically, but frequency of observation at the other stations is 1 time/day. It is expected that meteorological and hydrological condition will be observed 1time/hour and reflected to the plan and design of facilities.
0
Figure-1 Daily rainfall (Bhur observation station)- Observed river discharge Q1
0
Figure-2 Daily rainfall (Bhur observation station)- Calculated river discharge by rational formula Q2
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Cultivation method Crop Rice 472 933 1,977 14.5(Paddy), 30.5(Polished rice)*1
Spring rice 10 7 692 7.5 (Paddy)
Buckwheat 18 18 988 10
Fish pond 6
Mustard 2 1 556 Self consumption
Kitchen garden 62
Rice*2 6 22 3,70620(Paddy), 12(Polished rice)
Ginger 37 452 12,221 17 (now, 5 to 8)
Maize (March to June) 111 192 1,730 13
Maize (August to December) 75 103 1,369 13
Millet 28 28 988 15
Foxtail millet 36 27 741 Self consumption
Dal 57 28 494 50-60
Betel nuts 182 1,350 7,413 10 (usually traded in ton)
Ritch N.A. Self consumption
Banana N.A. Self consumption
292
Appendix-6.5 Summary of WUA workshop on the Taklai Irrigation System, Bhutan
Fallow Basic
information
Term of workshop 30th to 31st of January, 2012
528 (Registered No.), 778 (Estimated No.) 450 (Registered No.), 700 (Estimated No.) 78 (Registered No.)
Water Users Association （Chuzagang and Sershong）
CAFCO（Chuzagang Agricultural Farmers Cooperative）
BDBL（Bhutan Development Bank Limited）、CAFCO、Saving group 12
21 0 3,918
Champa, Kamtey, Kalobog (Jere), Kalobog (B), Ranjit→widely produced
MC Choti, Mota, Badur→produced by only a few farmers
Kamja-1,Kamja-2→widely produced Karjat, IR-64, BR-153→produced by only a few farmers
Varieties of rice produced on the scheme (Local varieties) Irrigable area when established (ha)
Irrigated area at the moment (ha)
809 533 Total area (ha)
No. of household
4,308 No. of household in Sershong
Varieties of rice produced on the scheme (Improved varieties)
No. of household in Chuzagang
Irrigation
*2: A variety has been disseminated to farmers cannot access to irrigation water called Bhur Kambja 1 and produced last year for the purpose of trial. The expected yield is 3,750kg-5,000kg/ha.
*1: Average price of Chuzagang and Sershong. In Chuzagang, paddy is 17Nu/kg and polished rice is 36Nu/kg. In Sershong, paddy is 12Nu/kg and polised rice is 25Nu/kg.
1st to 4th of February, 2012 29 (Male: 19, Female: 10) 45 yeas old
Chuzagang (High level): 11, (Low level): 10 Sershong (High level): 8
1.83 1.03 32hours/week 2hours/week Average cultivated area (ha) 1.03 Average production (kg) 2,370 Purpose for production
76% of producers target home consumption and 24% target both home consumption and marketing. On average, the 24% sell 589kg of paddy.
Marketing Mainly to CAFCO. Some household sell paddy to National Seed and Drukseed as seed paddy.
Average cultivated area (ha) 0.08 Average production (kg) 288
Purpose for production 14% of producers target home consumption and 86% target both home consumption and marketing.
Marketing Auction at Geleph
Average cultivated area (ha) 0.34 Average production (kg) 574
Purpose for production 84% of producers target for home consumption and 16% target both home consumption and marketing.
Marketing Locally
Average cultivated area (ha) 0.23 Average production (kg) 298
Purpose for production 84% of producers target home consumption, 11% target both home consumption and marketing and 5% target marketing.
Marketing Locally
Average cultivated area (ha) 0.20 Average production (kg) 23
Purpose for production 69% of producers target home consumption, 12% target both home consumption and marketing and 19% target marketing.
Marketing Mainly through middleman
Average cultivated area (ha) 0.04 Average production (kg) 57
Purpose for production Most producers target home consumption.
Average cultivated area (ha) 0.01 Average Production (kg) 7
Purpose for production Home consumption Average cultivated area (ha) 0.21
Average production (kg) 547
Purpose for production Most producers target home consumption.
Marketing Mainly through middleman
Average cultivated area (ha) 0.02 Average production (kg) 8 Average cultivated area (ha) 0.01 Average production (kg) 6 Purpose for production Marketing
Marketing Locally
Rice huller 10%
Rice milling machine 0%
Power tiller 3%
Cattle for drafting On average, each holder owns 2 cattle.
Harvester 0%
Rice planter 0%
Truck (ton capacity) 10%
Flower mill 3%
Pedal thresher 14%
Car 0%
No. of interviewees
Irrigation scheme interviewees belonging
Agricultural condition
Appendix-6.6 Summary of Household Survey on the Taklai Irrigation System, Bhutan
Average cultivated area (ha) Average irrigated area (ha) Irrigation hour (Summer) Irrigation hour (Winter) Basic
information
Term of Interview
Average age of interviewees
Others (vegitable, Oil crops and etc.)
Fish pond
No. of animals/household
% of household owing agricultural machinery and
Maize (March to June)
Maize (August to December)
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Tractor Plough Rotorvator
Rice huller 97%
Rice milling machine 3%
Power tiller 38%
Cattle for drafting 38%
Harvester 10%
Rice planter 0%
Truck (ton capacity) 10%
Flower mill 34%
Grazing (apply animal manure naturally) 97%
Pesticide 0%
Weedicide 31% (on average, 20kg are utilized) 79%
21 (1 person from each household)
Rice 86% household
Wheat 90% household
Vegitables on kitcken garden 79% household 7
8.4 4.4 8.4 5.4
Preparation of seedling, Up-rooting seedling, Transplanting, Weeding, Harvesting, Winnowing, Transporting
Ploughing, Land preparation, Making and clearing levee, Thresing, Transporting
Agricultural Machine (Nu) 3,300 Transportation Cost (Nu) 500
Others (Nu) 1,600 Lack of irrigation water 93%
Lack of labour 41%
Loss by wild animals 28%
Others 14% (lack of drinking water and transportation for marketing)
Assured irrigation 83%
Better access to agricultural machine 31%
Fence 10%
Others 10% (better access to drinking water and subsidy on agriculture)
WUA 97%
CAFCO 38%
Others 0%
% of household participating following agricultural cooperative and association
Social-economical condition
Annual living expenditure Nu/Month
% of household recognized following items as a problem on their farming
% of household recognized following items as a need
on their farming
Income form agriculture including rice production (Nu) Agricultural cost including rice produciton, livestock and fish production (Nu)
Benefit from other activities rather than agriculture (Nu)
45% (A set of a tractor, a plough and a rotorvator are lended by the CAFCO. )
Agricultural condition
Monthly living expenditure Nu/Month Average size of household
Net income (Nu)
Role of female on rice production
Role of male on rice production Income from rice production (Nu) Cost for rice production (Nu)
% of household sharing work with the others for rice production Average No. of members for work sharing on rice roduction
Minimum living cost needed Nu/Month
Annual comsumption of polished rice per family (kg) Amount of polished rice purchased per year・family
% of household borrowing agricultural machinery and
equipments
% of household utilizing agricultural inputs
Types of Crops farmers are willing to produce and % of
household desire
Items
Working hour by female in off season Working hour by male in cropping season Working hour by male in off season Working hour by female in cropping season
*1：Because most farmers conduct mixed cropping with Dal and Maize, the yield of Dal is relatively low.
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