Hey folks. I recently had a discussion with an acquaintance where we disagreed about the functions of media luna, specifically about the collective and dispersive impacts on surface water flow. Looking for papers or other writings about them seems to all point back to this document (PDF warning) with data that they work but not how they work. What follows is my understanding of the process, and any information that improves my understanding is greatly appreciated.

With "horns up", sheet flow slows as it encounters the obstruction - during the early parts of a precipitation event or flow event, this will cause the water to enter the root and unsaturated zones of the soil profile. The water that does not percolate into the soil continues to move at 90° to contour around the rest of the obstruction's parts while also moving downward due to gravity. As the soil moves towards its capacity for stored water, the percentage flowing through the media luna increases. The pressure from the water on the upslope side of the media luna causes the flow to disperse through the obstruction, the convex shape of which causes additional lateral movement of the water as it makes its way downslope. My intuition is that the additional resistance towards the center of the structure is part of the cause, along with an evenly distributed lower pressure gradient along the convex face.

With "horns down", the upslope water slowing capacity is similar (I would expect the water retention properties to be strongest when installed with stream banks to either side) but due to the concave nature of the shape there is a greater amount of surface area directing the flow of water towards the geometric center of the shape through the same physical processes noted above - gravity and pressure differentials. I am not strong in maths and am unsure of how greatly the pressure differential affects the water's course, but I expect that value is nonzero.

I have a sneaking suspicion that my friend was considering the upslope behavior of a less-porous obstruction while I was considering the downslope behavior of a more-porous obstruction, causing them to think I had the collection/dispersion effects backwards. I'm well practiced at being wrong though, so it's a possibility that I'm open to even if I'm not enthusiastic about it.

Thoughts?

Researchers from China have confirmed the existence of an approximately 8.5-year Inner Core Wobble (ICW) in both polar motion and length-of-day variations, revealing a static tilt of about 0.17 degrees between the Earth's inner core and mantle, challenging traditional assumptions and providing insights into the Earth's internal dynamics and density distribution.

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So how can we keep doing research in Antarctica while minimizing our impact on the environment? This question led to our new research published in the Journal of Environmental Management.

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This story is co-published with The Guardian and supported by The Heinrich Böll Foundation.

Andrée Nieuwjaer, a 67-year-old resident of Roubaix, France, is what one might call a frugal shopper. In fact, her fridge is full of produce that she got for free. Over the summer, she ate peaches, plums, carrots, zucchinis, turnips, endives — all manner of fruits and vegetables that local grocers didn’t want to sell, whether because of some aesthetic imperfection or because they were slightly overripe.

What Nieuwjaer couldn’t eat right away, she preserved — as fig marmalade, apricot jam, pickles. Reaching into the depths of her refrigerator in September, past a jar of diced beets that she’d preserved in vinegar, she tapped a container of chopped pineapple whose shelf life she’d extended with lemon juice: “It’ll last all month!” she exclaimed. Just a few inches away, two loaves of bread that a nearby school was going to get rid of lay in a glass baking dish, reconstituted as bread pudding. A third loaf was in a jar in the cupboard, transformed into bread crumbs that Nieuwjaer planned to sprinkle on a veggie casserole.

With everything she’d stocked up, Nieuwjaer was all set on groceries for the next few months. “I’m going to eat for free all winter,” she said in French, beaming.

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But Nieuwjaer didn’t just one day decide to join the movement; she was drawn into it as part of a local government experiment in waste management. In 2015, the city of Roubaix launched a campaign to reduce litter by teaching 100 families — including Nieuwjaer’s — strategies for cutting their waste in half. Similar efforts may soon be repeated across France as cities and regions begin striving to meet (and exceed) the country’s ambitious waste-reduction goals. At the heart of their efforts is a fundamental question: How do you get citizens to change their behavior?

read more: https://grist.org/international/in-france-zero-waste-experiments-tackle-a-tough-problem-peoples-habits/