Transcript Imperial College London

Water availability assessment
in data scarce catchments:
Case Study of Northern Thailand
Supattra Visessri
1st Year PhD Student, Environmental and Water Resource Engineering (EWRE) Section
Introduction
• Water is the most precious natural resource to the world.
• Imbalance between water supply and demand has caused
problems to the management and users.
• Frequent historical records of floods and droughts especially in
the north of Thailand.
• The four basins in the north of Thailand form the Chao Phraya
River Basin in which the capital and business centers are
located.
• There are few gauges in some subbasins especially along the
border of the basin thus introducing the problem of data scarcity.
• Regionalisation is needed to predict water availability and leading
to improved water management.
25 Basins of Thailand
12
24
19
21
6
18
15
13
1
16
22
10
7
4
8
2
11
3
20
14
23
5
17
9
25
25 Basins of Thailand: elevations above sea level
Current Methodology of Risk Assessment in Thailand
• Using aggregated measures of water abundance or scarcity.
• Primarily based on a monthly basis and lumped analysis.
• Low resolution of temporal and spatial analysis.
• The assessment is possible only where data are available.
Goal and Objectives
Goal
• To improve methodology for flood and drought risk analysis of large river
basins under data scarcity.
Detailed objectives
• To develop insight into various types of rainfall-runoff models i.e data
needs, uncertainties.
• To assess the applicability of models used to perform analyses of waterrelated risks under different environments and data scarcity condition.
• To select models and regionalisation methods which make use of the
data sets which are available.
• To test these models (quantify the uncertainty) and methods using a well
gauged pilot catchment, plus other less well gauged catchments.
• To evaluate impacts of climate change on water abundance and
shortage under data scarce conditions.
• To develop recommendations for future strategy at local level.
Research programme
• Phase I: Data assessment and determination of the study sites
• Phase II: Critical evaluation and selection of rainfall-runoff models
• Phase III: Regionalisation (Prediction of flow in ungauged basins)
• Phase IV: Climate change scenarios
Phase I: Data assessment and determination of the study sites
Phase I: Data assessment and determination of the study sites
• The most complete period of flow and rainfall data is
01/01/1995-31/12/2006 (12 years).
• The number of viable flow gauges with less than 35% of
missing record is as below:
Basin
Area
(km2)
Flow
gauges
Rain
gauges
Tele
gauges
47
63 (16)
12
Wang
33,898
10,791
5
18
0
Yom
23,616
14
32 (1)
0
Nan
34,330
23
51 (5)
0
Ping
* Numbers in brackets refer to the station with hourly rainfall.
Next step: Assessment of regionalisation method
• Regression method
Use regression analysis to find the relationship of parameters and
catchment descriptors (i.e. area, average precipitation, BFI) of wellgauged catchments. By applying the regression equations to ungauged
catchments, parameters of ungauged catchments can be obtained.
• Similarity method
Take parameter values of a well-gauged catchment without adjusting.
• Response Indices method
Find the relationship between response indices (i.e. mean daily flow)
and catchment descriptors.
Thank you