Environmental assessments (both EIA and IEA) on hydropower projects often pay very little attention on soil erosion in the upstream catchments since soil erosion is not an impact of the proposed project. Yes, in technical point of view, this argument is correct. However, soil erosion in the upstream catchment is a serious issue for viability of the proposed project. Therefore, we should control soil erosion in the upstream catchments after impounding reservoir of the project. Indeed, this could be proposed to the developer by the consultants to be done as a good practice. But, this is not a must and perhaps not legally bound. Therefore, is there any way to incorporate this issue into EIA or IEA reports in order to mitigate soil erosion in the upstream catchments?
I think we may consider the soil and water as a fluid with special viscosity in the upstream direction.as far as the total volume of the mix is relatively grater than the soil volume.
If you have rainfall data, soil, landuse and dem you can use USLE to estimate soil loss in the upstream catchment. Then use sediment delivery ratio to estimate sediment yield at the reservoir.
Now, to my answer, in the EIA report, impact to the Geology, Soil, land use, biodiversity and landscape is an factor or component. So, its the duty of the consultant to assess the impact to the these areas. If it is not included, I may say the consultant is failed to due justice to his duty.
It seems that previous responders have not properly understood what I posted in the question. Sorry for that, and I will elaborate the question further. There are so many techniques to measure or to estimate soil erosion rates in the upstream catchments. As Mashingia has indicated, application of USLE is one of the methods. My question is not about how the soil erosion is estimated or measured in the upstream catchments. The methods are known and it could be done simply. My question is about how the soil erosion in the upstream catchments is recognized as an IMPACT of a proposed hydropower project. If it were identified as a significant impact, we, the consultants, are permitted to propose measures for soil erosion to be mitigated in the upstream catchments. However, technically, soil erosion in the upstream catchments is not an impact of the proposed project. In the usual practice of environment assessment, it is difficult to rationalize soil erosion in the upstream catchments is an impact of the proposed project. During an assessment, first we look at the existing environment (physical, biological and social), then attempt to identify the possible impacts to the environment from the proposed project. In this context, the proposed project will not make any effect to the upstream area and soil erosion in the upstream catchments is not an impact of the proposed project. If so, logically, we are not able to suggest mitigations for soil erosion. However, on the other hand, soil erosion in the upstream catchments is an issue for viability of the project. Therefore, it is worthwhile to apply conservations in the upstream catchments for soil erosion. And I am thinking the ways that how we can grab this issue in our EIA reports. Any comment? Any suggestion?
In the long term the soil erosion in the upstream catchment area is going to affect the hydropower projects and therefore it is necessory that a consultant also should give suggestion and impacts by soil erosion in the upstream catchment in his EIA.
Dear Tilak.
.
The problem is not to use the techniques of sediment production upstream, the problem is that different techniques give EXTREMELY discordant values (errors of over 200% to 300%), so the engineers do not make fools of estimates so wrong.
.
Another problem is that with any change of land use (change in livestock for agriculture, for example), producing soil changes in DECADES.
.
Hint, use measures of sediment transport and if they do not exist, make measurements of sediment transport.
.
Dear Tilak.
.
Methods such as USLE, RUSLE and WEPP are developed for parcels (areas of tens or hundreds of m²), all phenomena that occur thereafter are not adequately quantified by these methods.
.
Please find a simple methodology related to this issue in the attached paper.
Article Paying the forest for electricity: A modelling framework to ...
In a EIA commissioned by me at IFAD for a reservoir in Pakistan we included upstream sediment load of the feeding river as cumulative impacts needs to considered as well in many EIA laws/regulations. Soil loss at the local level was calculated using USLE. Next we estimated at landscape level from the relief how much of the displaced soil from fields and other land cover/use types would end up as sediment in the river. Often it is wrongly assumed that all local soil loss ends up in the river and subsequently in the reservoir. Often a sizeable amount of the sediment is deposited elsewhere in the landscape. Ultimately we found that human-made erosion was insignificant compared with geological erosion in the (early) siltation of the reservoir. Rather than blaming the upstream farmers for a short lifetime of the reservoir, the forecasted sedimentation of the reservoir was underestimated by the proponents. This particular EIA dates back to the early 90s, but since then I observed the same phenomenon elsewhere (e.g. Tunisia).
- Badges
- Science topic
- Similar topics
- Geoscience
- Hydrology