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International Seminar on Biodiversity and Sustainable Development in the Mekong River Basin 42

5.3 % for the high RCP 8.5 scenario. In Lam Dong, the rainfall increases by 3.9 % for the RCP 4.5
scenario and 4.7 % for the high RCP 8.5 scenario In Dak Nong, the rainfall increases by 6.5% for
the RCP 4.5 scenario and 5.0 % for the RCP 4.5 scenario. With high scenario RCP 8.5 (NAWAPI).
According to the rain forecast table of meteorological stations in Gia Lai, Dak Lak, Dak
Nong and Lam Dong provinces in the SRB, the rainfall in summer and autumn mostly tends to
increase compared to the scenario. 1986 - 2005, especially the later periods tend to increase more
than the previous ones. In contrast, in winter, the rainfall in the period 2016 - 2035 decreased
compared to the period 1986 - 2005. However, the following periods are predicted to tend to
increase compared to the background period 1986 - 2005 (NAWAPI). The direct and indirect
impacts of CC on water resources in the SRB will likely lead to scarcity of surface water in the
dry season. Due to the lack of additional water sources, groundwater will be reduced in both
quantity and quality. In contrast, an excess of surface water in the rainy season will cause flooding,
surface erosion, and adverse effects on surface and groundwater quality (NAWAPI). In Gia Lai in
the dry season in recent years, most of the dams in the province have dried up, making production
and daily life extremely difficult. From October to the end of March every year, although the local
government always tries to pump water for trees, communes in the province still lack water in
many places. In fact, even the communes along the Ba river still lack water for many months of
the year. Many areas planted with coffee trees do not have enough water to irrigate, leading to the
trees withering and the people unable to save their property due to the lack of a reserve water
source.

Materials and methods
The Fuzzy AHP method is used throughout the study to assess the environmental
sustainability of irrigation water in the SRB in the context of CC. First, Fuzzy AHP is used to
design, from expert consultation to set up pairwise comparison matrices in the criteria, indicators
within the same criteria based on the questionnaire. Then analyze the consistency by analyzing
and checking the consistency of the matrices. Once the pairwise comparison matrix is consistent,
continue to calculate the relative weights of the components in the stable hierarchy using Fuzzy
AHP, thereby determining the overall weight of these components.
After synthesizing and analyzing information from sources, proceed to build a set of
criteria and indicators based on the existing status quo and arrange them in the form of a stable
hierarchical tree. The components of the hierarchical tree need to be clearly defined from the
highest level to the lowest level in order to concretize the common goal: sustainability criteria (SC)
and sustainability indicator (SI) in each respective SC.
Using the Fuzzy method AHP consults experts on pairwise comparisons between system
components on the same level and establishes reciprocal pairwise comparison matrices (IRCMs).
This can be done in the form of a questionnaire-based interview.
Fuzzy triangular transformation scale proposed by Chang (1996) with 5 linguistic variables
and the corresponding fuzzy triangle reciprocal scale is shown in Table 1. Equal ratings indicate
that the two attributes are equally important. A weak rating indicates that one attribute is slightly
more important than another. Strong ratings indicate that one attribute is more important than the
other. Very strong ratings indicate that one attribute is more important than the other. Absolutely
strong ratings indicate that one attribute is completely more important than the other. Each
language rating is given a corresponding fuzzy performance and corresponding fuzzy performance
based on the following rule:

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