In this post, I will address the use hydrological modelling to better carry out scenario planning and safeguard the sustainable delivery and integrity of the entire suite of freshwater 'umbrella' services.
Impact assessments
Impact assessments
Modelling potential impacts have been an important part of contemporary hydrological research. Studies may use models built for climate scenarios to simulate changes in river/flood regimes. Other studies may model potential changes by different irrigation development. I will assess both through modelling studies at the Inner Niger Delta and the Pongola basin.
The largest floodplain wetland in West Africa, the Inner Niger Delta is located downstream of the Upper Niger river basin which covers an area of >100,000 km2. The Inner Niger Delta is one of the most productive region in West Africa, supporting over 1 million people across the Sahel in 'river-dependent economies'. Ecosystem services include:
Hydrological Modelling
Using a semi-distributed conceptual model , river discharge were projected to decrease by 0.8% to >50% and flood extent can reduce by up to 50% by 2100 under a 2 degrees rise in temperature according to different GCM output (Thompson et.al. 2016). Projected changes to the river/flood regime through modelling therefore sheds light on the potential detrimental effects to ecosystem services within the basin. Reductions to peak flow would lead to a significant decline in available agricultural areas and may impact food security alongside increasing population pressures (Liersch et.al. 2013). Environmental flows analyses on ecosystem integrity using results from hydrological modelling would further provide information on the impacts climate change exert on ecosystem integrity and capability to provide and supply ES.
The Pongola River basin occupies an area of >7000 km2 in South Africa. Controlled releases of the Pongolapoort dam regulates inflow into floodplains, significantly impacting downstream provision and access to ecosystem services which were dependent on the natural peak/low flow regimes. Ecosystem services include: grazing, building, fuel wood, food production, biodiversity, flood attenuation, water quality control and cultural activities.
Hydrological Modelling
In order to adequately plan for future development scenarios to safeguard both ecosystem services and economic livelihoods, Lankford et.al. 2011 undertook hydrological modelling of 3 different flow releases scenarios to examine possible socioeconomic and ecological impacts.
Modelled findings indicate that scenario 1 would favour elites/powerful who are most likely to dictate flow releases, leading to decline in all identified ecosystem services. Scenario 2 contributes to poverty alleviation with minimal impacts to ecosystem services while encouraging diversification and sustainability. Scenario 3 contributes in the short term significantly to poverty alleviation and economic growth but causes decline in ecosystem services comparable to scenario 1 which may have substantial impacts in the long run (As seen in Lake Victoria).
Inner Niger Delta
Ecosystem Services
The largest floodplain wetland in West Africa, the Inner Niger Delta is located downstream of the Upper Niger river basin which covers an area of >100,000 km2. The Inner Niger Delta is one of the most productive region in West Africa, supporting over 1 million people across the Sahel in 'river-dependent economies'. Ecosystem services include:
- Agriculture (dams, irrigation schemes) - mainly for rice cultivation
- Fisheries
- Grazing (sheep, cow and goats)
- Hydroelectric power
- Wetlands regulating services (one of the world's largest RAMSAR site)
Future climate change is most likely to inflict substantial changes to the duration, timing, quantity and quality of river flow which will impact the integrity of these ES.
Hydrological Modelling
Using a semi-distributed conceptual model , river discharge were projected to decrease by 0.8% to >50% and flood extent can reduce by up to 50% by 2100 under a 2 degrees rise in temperature according to different GCM output (Thompson et.al. 2016). Projected changes to the river/flood regime through modelling therefore sheds light on the potential detrimental effects to ecosystem services within the basin. Reductions to peak flow would lead to a significant decline in available agricultural areas and may impact food security alongside increasing population pressures (Liersch et.al. 2013). Environmental flows analyses on ecosystem integrity using results from hydrological modelling would further provide information on the impacts climate change exert on ecosystem integrity and capability to provide and supply ES.
Pongola Floodplain
Ecosystem ServicesThe Pongola River basin occupies an area of >7000 km2 in South Africa. Controlled releases of the Pongolapoort dam regulates inflow into floodplains, significantly impacting downstream provision and access to ecosystem services which were dependent on the natural peak/low flow regimes. Ecosystem services include: grazing, building, fuel wood, food production, biodiversity, flood attenuation, water quality control and cultural activities.
Hydrological Modelling
In order to adequately plan for future development scenarios to safeguard both ecosystem services and economic livelihoods, Lankford et.al. 2011 undertook hydrological modelling of 3 different flow releases scenarios to examine possible socioeconomic and ecological impacts.
- Unstructured releases - poorly controlled releases
- Regulated releases with diversified economy - coordinated releases of water for both agricultural development and ecosystem services
- Regulated releases with single sector (agriculture) - full releases to support chosen agricultural development
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| Impacts to ES from Scenario (2) |
Hydrological modelling, although inevitably carrying a degree of uncertainty, allows for informed decisions regarding future management and justification for an alteration to current management strategies. Simulating hydrological processes under climate change or development scenarios, models are useful in assessing future changes to hydrological and ecosystem functioning which will have knock-on impacts to the provision of ecosystem services.
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