Key features of hydrographs

[@lizziewatson390]

really helpful video, thank you!!!

[@mrcta]

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[@GeogJuice]

Wow. That's quite a recommendation! Thank you

[@lukasmcewan]

gained a sub, thanks

[@GeogJuice]

Thanks for the sub!

[@seangeeling]

Appreciate your work here Mr Juice, this will definitely be useful for my class. I really must compliment your careful and clear descriptions, I can tell how much you must work on refining them. I would love to ask a question though, as I'm not sure the answer I gave in class was particularly enlightening... a smart student asked me why the base flow increases and touches the falling limb in the place it does. My answer was that soil throughflow and which would normally constitute the base flow of the river also increased during the event as the rainwater pushed the water in the soil through to the river - but I feel my explanation missed the point. Isn't base flow a sort of average level of the river? If so, how could it increase in this case? Thanks for your response in advance.

[@GeogJuice]

Thank you for comment and support. It is much appreciated. Baseflow is sometimes shown as a horizontal line, to reflect an average. However, baseflow is often shown as a rising line. The rising limb is fed by surface run-off, which reaches the river quickly over impermeable surfaces. The falling limb reflects how discharge is steadily falling once surface run-off has reduced/stopped. Water is now reaching the river mostly through the soil as throughflow, which is slower than surface run-off. Eventually, this flow stops and the river returns to normal conditions, receiving water slowly through the rocks as groundwater. The rising baseflow line in the hydrograph reflects that groundwater will have been recharged as a result of the rainfall event. This is conceptual, as it will be different for each river. Once the rising baseflow line reaches the falling limb of the graph (reflecting groundwater recharge), it now begins to fall reflecting the declining groundwater flow. Groundwater flow (baseflow) is now decreasing until it is recharged by another rainfall event. I hope this helps.

[@seangeeling]

@@GeogJuice Thanks for your response. So, the base flow line on this type of hydrograph rising steadily essentially represents the rising of the water table and it shows that the amount of water in aquifers and in general has risen thanks to infiltration from this event?

[@GeogJuice]

@@seangeeling The baseflow line in the hydrographs reflects a predicted increase in groundwater flow, as a result of infiltration during and following the rainfall event, contributing to baseflow/discharge. The water table may rise and aquifers may be recharged as a result of the rainfall event, but because this is related to a short period in time, I wouldn't emphasise that in my explanation.

[@seangeeling]

@@GeogJuice Got it. Thanks so much for taking the time to respond.

[@GeogJuice]

@@seangeeling You are very welcome