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International Seminar on Biodiversity and Sustainable Development in the Mekong River Basin 45

Results and discussion

Building indicators based on the VSRB actual water situation and data used
Indicators of environmental sustainability of irrigation water at SRB will be established
based on the consideration and assessment of all relevant factors affecting and affecting the
environment. The directives are developed to ensure environmental sustainability, by taking into
account the characteristics of the environment including quantity and quality of irrigation water
and the impact of natural disasters on the SRB environment.
Srepok is an area that mainly develops agriculture, the amount of water for irrigation is
very large. The total water demand for the whole Sre Pok basin in 2017 is 2,301.74 million m³, of
which the demand for irrigation accounts for the highest proportion of 1,946.52 million m³
(accounting for 84.57%) (VNMC, 2020). Therefore, the SI01 indicator is calculated by subtracting
the actual amount of water from the actual extraction and the potential amount of water to assess
the level of water exploitation to ensure the ability to supply enough water for agricultural
irrigation. In addition, water sources such as rivers, streams, ponds, lagoons and aquifers need to
be considered as a whole to calculate the components of water volume, thereby developing
appropriate water resource allocation planning options. Physical. Based on that, the SI02 directive
was developed to assess the sustainability of the flow, ensure the water supply regime of the river,
maintain the ecosystems and regulate when there is competition in water use. If the actual
Minimum Flow at the downstream station is greater than or equal to the Environmental Flow Rate,
the value of the indicator will be calculated by subtracting the ratio between the Environmental
Flow Rate and the Flow Rate. Actual minimum flow volume at the downstream station.
Conversely, if the actual Minimum Flow at the downstream station is less than the Environmental
Flow, the indicated value is 0, indicating the lower the sustainability.
The quality of surface water in the Srepok basin since 2002 until now has been polluted by
organic substances, nitrite and nitrate due to rainwater washing of surface substances along the
water flow into the river (Irrigation Planning Institute, 2013). At the same time, the NO3 indicator
- in some areas where the groundwater aquifer is exceeding the allowable threshold according to
QCVN 09-MT: 2015/BTNMT for example in Ia Drang sub-basin, Ea H'leo sub-basin, and Krong
Ana sub-basin,... (VNMC, 2020). Therefore, the value of indicator SI3 and SI4 is expressed by
subtracting the ratio between the Area of the polluted area and the Area of the whole basin, thereby
assessing the impact of pollution on environmental sustainability. Environment of the SRB,
ensuring the quality of irrigation water for agriculture. If the value of the indicator approaches 0,
it means that pollution has a great influence on the SRB environment, its sustainability is poor and
needs to be overcome, and vice versa if the value is gradually approaching 1. In the heavy rainy
season, flash floods, In the Srepok basin, a serious landslide occurred along the riverside,
narrowing the arable land. According to VNMC, the landslide area in the provinces in the territory
of the river basin is estimated at more than 1,207 ha and the land area affected by floods is more
than 30,500 ha (2017). In addition, in the dry season, high intensity drought often occurs. Some
districts such as Kbang, An Khe, Kong Chro, Krong Pa often suffer from severe drought with a
scale of several thousand to over hundreds of thousands of hectares per year, specifically in 2017,
the total area of drought crops in the provinces under the territory of the province. The watershed
area is estimated at 195,135.4 ha (VNMC, 2020). Therefore, three indicators SI05, SI06, SI07 were
developed to assess the impact of natural disasters on the environmental sustainability of the SRB,
by subtracting one from the ratio between the area affected by the natural disaster and ear and
Total area of SRB. If the indicator's value is gradually approaching 0, it means that the impact of

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