Chennai River Basin - Analyse the risk

Select area of interest in Chennai River Basin
Choose future scenario

1. Water scarcity risk

1.1 Study area

The coastal city of Chennai, the capital city of the state of Tamil Nadu, has a population of about 10.6 million people (census 2019). It is one of the largest cultural, economic, and educational centres of South India.

Chennai is also the largest industrial and commercial centre of South India, where the economy is anchored mostly in secondary and tertiary activities, such as automobile, software services, hardware manufacturing, financial services and textiles. Near the city Chennai, there are two industrial zones: Siruseri and Sriperumbudur. In additional to the two industrial zones, Muttukadu-Kovalam on the south is also a growing business area.

The unit of analysis is set as the sixteen subdistricts that are entirely within the basin boundaries and in addition, four districts that are partially included.

1.2 Risk per sub-basin

Water scarcity risk is visualized per municipality based on hazard (water gap), vulnerability , exposure components.

A risk score of 0 indicates lowest level of risk whereas 1 is the highest. Results shown for a selected time-period and a user group.

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1.3 General observations

  • Water scarcity risk gradually increases over time accross all sectors and at almost all sub-districts. Risks becomes particularly high after 2040.
  • One major driver of increasing water risk is increasing hazard, especially in terms of increasing frequency and persistence of water gap events.
  • Accross the domestic sector, the rural population below the poverty line faces greatest risk from water scarcity, in particular after 2030.
  • Risk for the agriculture sector is low, even after 2040. In comparison, industry faces increasing risk from water scarcity beginning with the 2030-2040 period.
  • Results are comparable accross both SSP2 and SSP3 scenarios.
  • The overall water scarcity risk in the domestic sector increases in both scenarios.
  • Population groups below the poverty line are shown to have the highest risk, especially after 2030. Rural population under poverty line is highly under risk, especially in several districts such as Nedungundram.
  • The overall water scarcity risk for the agricultural and industry slightly increases over time in both SSP2 and SSP3 scenarios*
  • Water scarcity risk slightly increases over time, however the magnitude of risk for 2050 is low (score < 0.4)
  • Risk for the industry is higher in comparison to the agriculture, and especially some sub-districts give high risk after 2040 (> 0.6, shown by orange color).

2. Risk Assessment

2.1 Calculation approach

The WaterLOUPE water scarcity risk analysis shows the relative risks for the different sectors and user groups, now and in the future. The presented risk level of the area is the result of a combination of the hazard (drought conditions, reduced water availability), the exposure of water users in different sectors (domestic, nature, and economic) and the vulnerability levels of the different water users in the basin.

Risk is expressed through the Water Scarcity Risk Index (WSRI), as a standardized measure of risk that can range from 0 (low or no risk) to 1 (maximum risk) at district-level and per consumer group/sector.

WSRI index score is calculated by aggregating hazard, exposure and vulnerability scores, each quantified first separately.

2.2 Main users and resources

This chart provides information about water demand for the different sectors as well as the water availability for the selected sub basin. The information is averaged per 10 years.

2.3 Water gap over time

This graph shows the total demand and availability for the selected sub basin and scenario over time. The graph presents monthly averages of water availability and demand.

2.4 Water gap index

This map summarizes the water gap index scores of each subdistrict for the current (2010-2020) and future conditions through the color scheme from red (high hazard) to green (low hazard).

Calculated water gap scores are generally low (< 0.4) accross the entire basin indicated by the dominance of the green color.

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2.5 Exposure

Exposure to water gap is shown on the left, with a color scale ranging from red (highest) to green (lowest). Results are shown per sector.

Spatial variability of exposure is highest for the agriculture sector and the rural population above poverty line. For the remaining groups/sectors, exposure values are similar accros all sub-basins.

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2.6 Vulnerability

  • Water scarcity risk gradually increases over time accross all sectors and at almost all sub-districts. Risks becomes particularly high after 2040.
  • One major driver of increasing water risk is increasing hazard, especially in terms of increasing frequency and persistence of water gap events.
  • Accross the domestic sector, the rural population below the poverty line faces greatest risk from water scarcity, in particular after 2030.
  • Risk for the agriculture sector is low, even after 2040. In comparison, industry faces increasing risk from water scarcity beginning with the 2030-2040 period.
  • Results are comparable accross both SSP2 and SSP3 scenarios.

3. Solution Strategies

3.1 From risk assessment to solution strategy

A next step when improving the water security in a basin, is the development of water scarcity solution strategies with all stakeholders. The solution strategies are expected to improve the water security at short to medium time scales, but should also enable the possibility to adapt to future changes (both climatic and socioeconomic).

In the first phases of the development of solution strategies, the results of the water scarcity risk analyses provide information to prioritize areas, sectors, and user groups with high risk and basin characteristics needed to evaluate the technical, environmental, financial, economic and political suitability of measures in that specific basin.

3.2 Developing solution strategies

To compose a water scarcity solution strategy, various mitigation and adaptation measures need to be combined. To evaluate the suitability of measures for the specific basin information about their physical, environmental, socio-economic, and political characteristics context should be clear to all stakeholders.

WaterLOUPE 2.0 contains an information catalogue that provides such information for a range of water scarcity solution measures. The information catalogue can be viewed here.