Reservoirs silting up

This gives a good explanation of a world wide problem, I have seen a number of reservoirs that have been filled with silt.

This is a major reason why lots of small, low-capital dams high up in the landscape (Yeomans style) make far more sense than big, main-stem river blockages. Dredging a small dam on a farm isn't an awful job in the dry season and as a bonus you get high-value material that can be returned to the soil...and if you're managing the land well, that might never need to happen.

Phil Yeomans style dams cannot supply town warer. Or irrigation.
Here is some interesting information about reservoirs being useless because of siltation.
http://www.hcn.org/articles/water-as-sediment-builds

If you did an entire catchment with keyline swale systems and small, high dams for storage, you could recharge the aquifers to the point where lots of town supplies could be met with bore water. That's the whole point of Yeomans' method...getting the water into the ground slowly instead of having it run off into the nearest drainage (with a full load of topsoil).

But that really only scales up to towns. A big part of the problem is that we have huge cities and entire regions dependent on massive dams and as the reservoirs lose capacity, the effective storage and carryover period shrinks. Put that together with deeper and longer droughts, interspersed with crazy flood events, and places like the US southwest will need to rethink their population density.

I think we need to adopt a different frame of mind about these problems.

We've spent a century or two building up a whole society based on short-term thinking (booting the problem to the next generation, i.e. now), enormous scale (sexy and powerful at the beginning but bringing equally enormous problems over time), and concentration -- of wealth, of water, of topsoil, of information systems, of human population, etc.

We are collectively driven to these unsustainable solutions, and because someone finds them economically "efficient" at a given moment we keep on taking this course. Even though the time of reckoning has already arrived, and we are trying to solve the problems created over the last 50 or 100 years with dwindling natural resources, grandiose decaying infrastructure, and decreased knowledge of natural systems as humans are now mostly urbanites who get our information via TikTok rather than our own eyes and hands.

I sometimes think of the mentality of many (or all?) groups of North American Indians by way of contrast. The "seven generations" principle of the Iroquois, the plains Indians carefully managing how many buffalo they harvested at a time in order to keep the herds bountiful, and many more examples. Perhaps because they didn't have a boss worried about quarterly profits telling them what to do and they didn't keep GDP statistics, they made normal, sane decisions that seemed to reflect a deep knowledge of how nature actually works, and complete respect and care for future generations.  They were investing in nature rather than mining it for short-term personal gain or grand visions of empire.

Permaculture, for me, is a way of looking at whole systems and infusing a bit of the spirit of wisdom and sanity of many indigenous cultures into our Western tech-centered mentality. "How does nature solve this problem?" is a great question.

Phil makes a very good point. With people on the land, and being sensitive to it, they can restore water cycles, recharge springs and aquifers, green the desert, restore clear-cut rainforest, etc.

I think in the end we'll have to change our way of thinking and our way of life. Eventually we will need loads of people all over the land taking responsibility for managing their little bit of nature with a view to restoring working natural systems rather than trying to tweak the problematic infrastructure that our old way of thinking created. That's what permaculture thinking has brought me to think, anyway.

For small-scale systems, where possible it's good to design in a de-silting pond or two on the way into a water storage pond. They can be relatively small and dredged frequently, using the fertile topsoil they contain on your farmland. A big dam I wouldn't know what to do with, there are so many big-industrial problems rolled into that dilemma.

I watch the top video and think, what to do with all the glyphosate and other toxic gick in that silt, even if you dredge it? I don't know and personally I'd rather work on creating practical alternatives to that whole dysfuctional system.

Just saw a post out there on the internet that illustrates one solution to this problem that already exists:

(oops, image link didn't work, see photo below)

source

OK, everything on that website does need to be taken with a grain of salt, but still, the photo shows a beaver dam's ability to hold back silt. Beavers are great topsoil builders and you can see why. I keep getting more and more convinced that nature already solved all our problems ages ago, it's just waiting for us to notice.

In any case, my mind always goes to de-silting ponds on the infeed to avoid silting, so it's nice to have another alternative to explore to help keep your pond water clear.

Reducing silt inflow certainly does help, in the sense that it delays the inevitable. The problem is that most large-volume reservoirs are in steep landscapes - because of the shape of the land and the presence of rainfall make for cost-effective investments - and those environments are by definition highly erosional. I would suggest that the majority of reservoirs are likely supplied by fast flowing mountain streams and rivers rather than meandering rivers in floodplains as seen that that image. I think that is likely the case in the UK at least, based on the dams I have seen.