Challenge of runoff regulation to supply paddy terraces in Subak irrigation schemes. Introduction. Paddy terraces are typical landscapes of Subak irrigation schemes in Bali Indonesia. Bali has 5630 km 2 area, and 57 % have topography slope between 15 % - > 40 %
A Subak irrigation scheme, primarily in Bali Indonesia is an irrigation scheme of which the construction, operation and maintenance is based on agreed principles of technology, management of agriculture and religious community
Ulun Carik Temple
Subak irrigation schemes are based on the continuous flow system (tektek/kecoran).
Cathment area : 123.75 km2
Main river : 35.5 km
Irrigated fields : 5,268 Ha
Telaga Tunjung Dam
The Generas of Subak Agung Yeh Ho
In Yeh Ho irrigation schemes, the cropping patterns which fall on specific months have been determined and agreed by Subak
For many centuries, this cropping patterns have been used and believed as a fair system of water distribution
The main objective of this study is to analyze runoff regulation.
This analysis can support the system arrangement of water supply to paddy terraces in Subak irrigation schemes in order to sustain agricultural productivity at upstream, midstream and downstream level.
Empirical flow frequency analysis
A popular method of studying the variability of stream flow is through flow duration curves which can be regarded as standard reporting output from hydrological data processing
(DHV Consultants BV & Delft Hydraulic, 1999).
The Weibull formula
A compromise with more statistical justification. If the n values are distributed uniformly between 0 and 100 percent probability, then there must be n + 1 intervals, n – 1 between the data points and 2 at the ends(Chow, et.al, 1988):
The analysis procedure is as follows:
The advantages of Weibull analysis are in the ability to provide reasonably accurate failure analysis and failure forecasts with extremely small samples, as well as provide a simple and useful graphical plot, which is important to engineers and managers (Robert B. Abernethy, 2002) .
In above analysis, there is the seven weirs, however, only have complete data collected from the year 2002 – 2010.