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The challenge of managing water resources under uncertainty

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REACH Conference on Water Security and Poverty
breakout: Managing climate resilience
Thursday 28 March | 11:00-12:30
Presenter: Dr. Meron Taye, Water and Land Resource Centre

Published in: Environment
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The challenge of managing water resources under uncertainty

  1. 1. The challenge of managing water resources under uncertainty Meron Teferi Taye, REACH Ethiopia program manager Water and Land Resources Center Insert image here. Do not compress to fit the size. Instead, use the cropping tool (found under the format tab). Increase the size of the image proportionally until it fits the width of the slide, then crop to decrease the height.
  2. 2. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford Challenges of climate variability • Awash is a basin of extremes – Awash is a great example of uneven distribution of water in space and time. • Temporal variation – Wet season (kiremt) brings devastating floods and dry season causes water scarcity and droughts. • Spatial variation – Upstream areas (highlands) receive on average 1600 mm rainfall/year while downstream areas (lowlands) barely get 100 mm rainfall/year 14 16 18 20 22 24 26 28 30 0 20 40 60 80 100 120 140 160 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Temperature(°C) Monthlyrainfall(mm) Rainfall Temeprature Kiremt Belg
  3. 3. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford Water availability per capita • Water availability per capita of Ethiopia is reaching the absolute water scarcity threshold, 1000 m3/capita/year – But in Awash basin it is already under this threshold at 325 m3per person/year (Adeba et al. 2016). • Annual variability of rainfall in the Awash basin – The last decade experienced below average years mostly. -40% -30% -20% -10% 0% 10% 20% 30% 40% 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 Precipitationanomaly(%) Year Awash 0 20 40 60 80 100 120 0 2000 4000 6000 8000 1950 1970 1990 2010 Populationnumber(inmillion) Water/capita/year(m3) Year Water per capita Threshold Population
  4. 4. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford • For the graph in previous slide we can have decreasing trend only if we start after 1984, still it won’t be significant • But the years after 2007 there are more drier years • Couldn’t find data on awash population as timeseries, anyone? To be deleted y = -0.0021x + 0.0346 R² = 0.0277 -40% -30% -20% -10% 0% 10% 20% 30% 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
  5. 5. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford Climate change threat • Long term planning in the basin is also threatened by climate change – Temperature is increasing under all climate scenarios – The area covering the Awash basin shows mean temperature increment of 1.5°C to 3°C in the coming decades until 2100 • This will have implications on precipitation and water resouces Source: KNMI climate explorer, 2019
  6. 6. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford Climate change impact uncertainty • Estimating the impact of climate change impact on water resources requires several steps. – Climate models, downscaling methods, hydrological models • At all these steps there are sources of uncertainty that influence the climate change impact estimates on water resources
  7. 7. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford • Challenge of data availability and reliability is one of them – Stream gauges are scant as we go down to the downstream of the basin – Not so much information is available on water abstraction • Using methods/tools that deal with low data availability is important in climate change impact estimations to reduce uncertainty sources Climate change impact uncertainty
  8. 8. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford Climate models evaluation • One source of uncertainty comes from the climate models. • Analysis was done to find out ability of models at reproducing the historical climate. – Four metrics were used including: Seasonal cycle, Trends, Mean bias, and Variability • Three climate models met the selection criteria – This were used to find out the projections for hydrological variables
  9. 9. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford Impact on hydrological variables • Temperature projections – Consistent increasing trend until the end of the century • Precipitation projections show different signs for different months. – April is drier than the rest of the months with precipitation decrease of 24% on average. – May is projected to be drier by 14% on average. – June to August projected on average increase in precipitation of 4%, 9%, and 6%, respectively. Mid future (2031–2055) precipitation projections
  10. 10. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford Impact on hydrological variables • Changes were evaluated at scale of multidecadal mean water availability averaged over the basin area – 𝑊𝐴 𝑚 = 𝑃𝑚 − 𝐸𝑇 𝑚 – 𝑊𝐴_𝐶𝐹𝑚 = 𝑊𝐴_𝑓𝑢𝑡 𝑚 − 𝑊𝐴_ℎ𝑖𝑠 𝑚 – Note that this is not streamflow at outlet of the basin • This estimate or tool shows projected climate signal over the basin for long term planning – Ignores the complexity related to population dynamics, abstraction, etc. – It’s singles out impacts only due to climate change
  11. 11. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford Impact on hydrological variables • April to June are projected to face more intense water stress than the rest of the months – Due to decreasing precipitation and increasing temperature • April to June are critical for irrigators – Data from Awash basin authority on crop water requirement for 23 farms in the basin demonstrate highest requirement in May • This water stress is a potential conflict source among irrigators – Also between sectors such as hydropower and irrigation 0 1 2 3 4 5 6 7 8 9 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Meancropwater requirement(m3) Millions
  12. 12. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford • Additional climate risk metrics are being mapped to look at seasonal scales with prolonged extreme events or consecutive dry seasons are being mapped by: – Counting the number of times there are seasons that are lower than a given threshold consecutively representing consecutive dry seasons – In the figures, 1 Standard deviation below average rainfall is set as a threshold for 1981-2017 period for selected consecutive seasons – Consecutive dry Belg- Kiremt seasons are more common in the eastern part of the basin Additional climate risk metrics Belg-Belg Kiremt-Kiremt Belg-Kiremt How much stronger or probable such events will be can be estimated from climate models projection (ongoing work)
  13. 13. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford • The basin has both climatic risks and decision making risks – Short term, long term, temporal and spatial variability • The climate signal tool provide information for longer term planning • Dry season water shortage/stress is projected to increase in the future as a result of climate change in the Awash basin – Note that uncertainty in precipitation is still a challenge for our region. But uncertainty by itself is an outcome that water managers should be aware of and plan towards strategies that work under a range of scenarios Planning with uncertainty
  14. 14. REACH Water Security and Poverty Conference 27-29 March | Keble College, Oxford • Sustainable and collaborative water allocation systems, efficient water use mechanisms need to be in place – This calls for better coordination of upstream and downstream water managers and users • The need to refine our knowledge on the basin’s resource base is still paramount – Understanding groundwater helps to set up climate resilient water supply systems (ongoing work on GW in Awash) Planning with uncertainty
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