Climate change and Impact on Irrigation Management. Framework for Resilience of Irriga3on Systems in Nepal Umesh Parajuli

Transcription

1 Climate change and Impact on Irrigation Management Framework for Resilience of Irriga3on Systems in Nepal Umesh Parajuli

2 Contents of presenta3on 1. Basic concepts 2. Findings from field studies 3. Adaptation measures 4. Conclusions

3 Concept: Climate change & its consequences Climate change Human intrusion in NR Changes in Temperature Intensify hydrological cycle Changes in precipitation Changes in: Water availability Sedimentation / land slides Changes in ET 0 and bio mass production Impact on Irrigation

4 Impacts: increase in temperature Impact Negative impact Positive impact Description 1. Evapotranspiration will increase (with every 1 C rise in temp. ETcrop will increase by 6-7 %) 2. Loss of some plant varieties due to their inability to cope with rising temperature 1. Biomass production and consequently crop yield will increase 2. Cultivation can be possible even in higher altitude

5 Changes in precipitation / hydrological cycle and likely risks / impacts on irrigation Risks Flash flood Change in seasonal water availability Drought Landslides & sediment flow Storms and hailstones Impacts Physical damages to infrastructure Inundation and sedimentation Erosion & landslides Reduction in dry season water availability Fluctuating water availability monsoon (intermediate dry spell and draught) Loss of crops due to long dry spells Physical damages to infrastructure, and sedimentation in canals / rivers Loss of crops

6 Field observa3ons

7 Changes in floods and flooding There are evidences of increasing peak floods in rivers Examples are:

8 Flood level in July 2016 Eroded steel capping Rolling boulders Sringeghat Diversion Weir

9 Changes in precipita3on Long term climatic data suggests no defined past trends in rainfall pattern Farmers, however, feel that rainfall is decreasing Farmer s perception may have been derived from their judgment of how well rainfall meets agricultural needs for water

10 Rainfall characteristic: Days with week long dry spell Frequency (Monthly) y = x R² = June Linear (June) Frequency (Monthly) y = 0.008x R² = Sept Linear (Sept)

11 Rainfall Characteristics Decreasing trend of light rains (< 50 mm), and increasing dry spells during critical periods may support supports farmers perceptions on decreasing rainfall

12 Changes in river water availability Dry season low flows in rivers (lps) Year Locations Girwari U/S of all intakes Banganga U/S, Banganga Barrage This suggests that dry season flows in rivers are decreasing substantially This is applicable in canal flows as well

13 Canal flows at specified locations in 1997 and 2016 Canal flows in lps Canal flows U/S of the main proportionating weir 7/24 7/26 7/28 7/30 8/1 8/3 8/5 8/7 8/9 8/11 8/13 8/15 8/17 8/19 8/21 8/23 8/25 8/27 8/29 8/31 9/2 9/4 9/6 9/8 9/10 9/12 9/14 9/16 Dates Canal flow 2016 Canal flow 1997 Canal flows in lps Canal flows U/S of proportioning weir at Basantapur 7/23 7/25 7/27 7/29 7/31 8/2 8/4 8/6 8/8 8/10 8/12 8/14 8/16 8/18 8/20 8/22 8/24 8/26 8/28 8/30 9/1 9/3 9/5 9/7 9/9 9/11 9/13 9/15 9/17 Dates Canal flow 2016 Canal flow 1997

14 Other observa3ons Infrastructural improvements enhance reliability and efficiency of water delivery, which in turn helps in developing climate resilient irrigation systems. Construction of weir across a river has a wider impacts downstream Mining of riverbed materials has changed river morphology threatening the stability of traditional irrigation intakes There are evidences that with declining availability of irrigation, farmers are cultivating paddy under deficit irrigation leading to higher risks of crop production

15 Examples: 400 Irrigation balance, 100 Julphe IS 0 Water volume (000 m3) Irrigation balance, Julphe Sub-system June IV July I July II July III July IV Aug I Aug II Aug III Aug IV Sept I Sept II Sept III Sept IV 500 Irrigation balance, Basantapur sub-system June IV July I July II July III July IV Aug I Aug II Aug III Aug IV Sept I Sept II Sept III Sept IV Water volume (000 m3)

16 Irriga3on balance: Singeghat IS Irrigation balance, Baijalpur Irrigation balance, Bathanpur Water volume (000 m3) Water volume (000 m3) June IV July I July II July III July IV Aug I Aug II Aug III Aug IV June IV July I July II July III July IV Aug I Aug II Aug III Aug IV Water volume (000 m3) Irrigation balance, Jhanda June IV July I July II July III July IV Aug I Aug II Aug III Aug IV

17 Ongoing adaptation measures 1. Changes in irrigation and agricultural practices 2. Improving coordination between systems along a single river leading to river basin based management of irrigation 3. Diversification of water sources through the development of tube wells where possible 4. Improving institutional & infrastructural arrangements for better water control

18 Conclusions Climate change does have influences on irriga3on system and its management. But, it is not the only agents for changes. Other important agents are: Ø Increasing water uses upstream due to increasing popula3on Ø Changing socio-economic situa3ons of local community, and Ø Mining of riverbed materials leading to changes in river morphology

19 Thank you