Local Recharge and baseflow analysis

We used the SWY to model the impact of forest restoration actions under future climate conditions (evapotranspiration and precipitation). The results show that the restoration actions decrease in local recharge (L) and baseflow (B) as compared to a business-as-usual scenario without restoration. We are explaining these results by highlighting the increase in evapotranspiration and the possible increase in water uptake by plants. These results do not necessarily imply that forest restoration is not a good strategy for climate change adaptation strategies, as forest restoration impacts “rainfall pattern regulation services” with higher evapotranspiration positively impacting terrestrial rainfall.

Do you have any other ideas or advice to help us explain the results?

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Hi @Guille ,

Thanks for writing in to the forum and sharing your experience. The research sounds interesting!

I would have to see your data to be able to accurately interpret the impacts of changes between scenarios on your results. Typically, when forests are restored, I’d expect less QF and more L and B, but it depends on how your biophysical table is parameterized for each LULC class. Please feel free to attempt to share those data here if you’d like us to examine the Kc and CN values so we can speculate on how your changes may have affected the differences in your results.

-Jesse

Hi @Guille,
It is true that forest restoration can impact the water balance in an area in complex ways, depending on what kinds of assumptions you are making about the restored areas (are you restoring with native species? with plantation forest? with passive regeneration?). If evapotranspiration of the restored vegetation is higher than the current land cover on an annual basis, then you could indeed see a shift in the water balance from Q, L, and B to evapotranspiration.

I am curious if you are seeing this decrease in L and B on an annual scale, or is it also true for all months of the year? Sometimes we see that the annual pattern is an overall decline in water yield, but seasonal patterns can show either increases or decreases, sometimes with a decline in runoff during rainy seasons but an increase in baseflow during dry seasons. See, for example, an excellent review by Filoso et al. 2017. Further, Dib et al. 2023 discuss these complex dynamics, including the contribution of evapotranspiration to rainfall in downwind areas as you suggest.

There is also a wealth of literature that supports forest restoration as a climate adaptation strategy, beyond its water quantity implications - for wild harvest forest products, carbon sequestration, temperature regulation, pest control services, water quality regulation, etc. In your case, If you are confident that your parameterization of the LULC changes in the model are correct (specifically CN and Kc), then it would be worthwhile to consider that while forest restoration could have multiple climate adaptation benefits for your study area, land managers shoud be very cautious in the selection of restoration strategies and locations because of the potential impact they could have on water availability.

~ Adrian

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Hi Adrian,

Thanks a lot for your reply and for pointing out the references by Filoso et al. (2017) and Dib et al. (2023)— very useful!

Indeed we are seeing the decrease in L and B on an annual scale. I noticed that we have monthly QF (quick flow) in the SWY intermediate results, which should be useful for examining seasonal dynamics. However, it seems that monthly data for B or L isn’t directly available, which limits our ability to assess how these components vary throughout the year.

I’ll be looking more into this and will keep you updated on our progress. Thanks again for the valuable insights!

Guille.

Hi Jesse, thanks a lot for your help.

I will try to share the BT data later on… For now, I would like to point out that we are using values from literature. Concerning Kc, we are using FAO data and in general, the Kc for trees is higher than for crops.

Yes, you are right that the model does not output B or L at the monthly scale, which were not included because the model does not track movement of water through the subsurface at a monthly time step. However, the AET output is available at monthly level, which could be used along with QF to understand the impact of forest restoration on water that is being “taken out” of the system via AET, and in which months this effect is most significant.

Best,
Adrian

Hi again, Adrian,

Thanks for the clarification. We also have annual AET in the intermediate outputs, though I only see monthly results for modeled reference evapotranspiration (with et0 prefix) and QF.

Additionally, I was wondering if you think there might be an opportunity to link AET to rainfall pattern regulation services at a sub-continental scale, even though these services are not directly modeled by InVEST. I would greatly appreciate your thoughts on this.

Best,
Guille.

Hi Jesse and Adrian,

We still have a few questions regarding the interpretation of the SWY results. Would it be possible to arrange a virtual meeting with someone from your team to discuss this further?

Thank you for considering this! @adrianvogl @jesseG

Best,
Guille.