How does dredging help the rivers that have gone dry? If you dig deeper, that small, and fixed, amount of water is just going to go lower, isn't it? That just what my layman's logic says, at least. And if it doesn't address the problem, which is not enough water, then why do they do it (or at least, plan to, for example, in Germany)?
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1$\begingroup$ Do you a reference for that? Until your question, I wasn't aware it was happening. Just inferring from your question, it might be easier to dredge the rivers now, with little or no water so that when the water eventually returns they will have a deeper & more navigable river. Or they may want to clear choke points in the river. $\endgroup$– FredSep 15, 2022 at 1:05
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1$\begingroup$ Not an expert, so it's just an idea: maybe if the water is spread over a wider but shallower channel, it has more area exposed, thus more evaporation? While a deeper/narrower channel would have less evaporation due to lower area exposed? $\endgroup$– Jean-Marie PrivalSep 15, 2022 at 7:57
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1$\begingroup$ The linked news story suggests that dredging is proposed to increase navigability of the rivers and not to address the low flow. $\endgroup$– Andy MSep 15, 2022 at 9:23
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1$\begingroup$ the groundwater level is often close to the water level in rivers so by dredging one can avoid the river running dry by using the inflow from ground water to keep the river flowing,it is far from an ideal solution as a dropping groundwater level will have a negative effect on the surounding area. $\endgroup$– trond hansenSep 15, 2022 at 9:43
1 Answer
Actually, it's about access to the water table. If the water table is under the river, it can be accessed by dredging. Either way, it's just a last resort for totally anomalous weather.