The Gap in the Nets
A hamlet of 46 people pays for a tanker every eleven days and wants fog nets. Two pilot sites a hundred metres higher and lower give 5.2 and 2.3 litres per square metre per day. The ridge wins, until an old goatherd says the nets will drink the fog his grove lives on. The story is about one drop in ten, a rule written before the data, and a forty-metre gap left open on purpose.
Dionisia Huamán had been the cooperative's secretary for nineteen years, and in all that time the water had arrived at Santa Rosa de las Lomas in the same way, on the back of a tanker lorry that smelled of diesel and wet rubber. It held ten cubic metres. It came every eleven days when the road was good and every nineteen when it was not, and the driver counted the hoses before he let the first litre out.
There were forty-six people in the hamlet, in twelve houses and a chapel. The cooperative's rule was fifteen litres a day each, for drinking, cooking and washing hands, and everything else was done with whatever came off the roofs in the four wet minutes of a year. Dionisia had worked out once, on the back of a seed-company calendar, that the rule came to 690 litres a day and about 252 cubic metres a year, which was twenty-five tankers. She had pinned the calendar to the wall of the cooperative office. She did not look at it often. She knew what it said.
In June of 2049 the cooperative bought four square metres of fog net, a roll of black polyethylene mesh and a set of poles, with a grant from the diocese's water fund and a tablet that came with it. The tablet's assistant was called Garúa, which is what the people of that coast call the grey, wet, low sky that sits on the hills for half the year and never quite rains. It had been set up by Marisol Condori, who was twenty-four and had come home from the engineering school in Arequipa for a year because her mother was ill. Marisol did the poles. Garúa did the figures. Dionisia did the arguing.
"Two sites," Marisol said, the first night, with her finger on the map. "The ridge, at six hundred and forty metres. And the cemetery wall, at five hundred and twenty. Two nets at each, one square metre each, with a trough and a bucket. We read the buckets every morning."
"Why would we not simply put them by the houses?" Dionisia said. "The cemetery wall is by the houses."
"Because the fog is not the same everywhere," Garúa said. "It is a layer, a deck of cloud that sits between about four hundred and eight hundred metres in the cold season. The water is not spread evenly through it. I do not know yet which of the two places is better, and I would rather measure than say, because the answer decides where you spend the diocese's money."
Dionisia, who had once spent eight months waiting for a government engineer to say what she could have told him in an afternoon, folded her arms and let it measure.
Here is what was true in 2026, when this story was written, and what had been added by 2049.
Fog collection is old and simple. A mesh is hung across the wind. Droplets too small to fall carry on the air until they meet a thread, stick, join, and run down into a trough. The standard test instrument, described by Robert Schemenauer and Pilar Cereceda in work from the 1980s and 90s, is a flat square metre of Raschel mesh, and a collector of that size is what the cooperative buys in the story. Near El Tofo in Chile such collectors gave about 3 litres per square metre per day averaged over the year, and far more on the best days. Yields of 2 to 10 litres per square metre per day in a fog season are what a careful reader finds in the published sites on the coasts of Chile and Peru. Large collectors, forty or so square metres, give a good deal less per square metre than the standard one. The 0.7 that Garúa uses below is a guess, and the story says so.
The lomas are real. They are seasonal plant communities on the fog-fed hills of the coastal desert of Peru and northern Chile, with grasses, bulbs, shrubs and in some places groves of tara, a small leguminous tree. The water they live on is the same fog the nets drink. Whether a row of nets measurably dries the plants downwind is not settled, and it depends on the slope, the wind and the mesh. It is the right question to ask, which is why the nets in this story are put in with a measuring rule rather than a promise.
What had been added by 2049 was a tablet that could keep a gauge book, say what it measured and what it assumed, and refuse to quote a village's water as a number it did not have. The rest is arithmetic a person could do on a calendar. The hamlet, the people and the grant are invented. This is not engineering advice.
The first week of readings were good and the second were better. On the ninth night the wind came out of the south-west at about fourteen metres a second, and in the morning one of the ridge nets was lying across the track with its poles snapped out of the ground like a row of teeth.
Marisol did not say a word for a minute. Then she said, "I set them sixty centimetres. That is what the video said."
"The video was for a square metre in a garden," Garúa said. "It is a reasonable first depth for a net held up by one person. The other ridge net and the two on the cemetery wall, which is in the lee of the hill, are untouched. I would like to lose nothing more than that one net's readings for the nine days. I suggest the poles go in a metre and twenty, with stays to the rock, and that we say in the book that the ridge reading has a gap from the ninth to the eleventh night."
They reset it. Dionisia said that a metre twenty seemed to be about what she would have expected the video to say.
By late September there were ninety-six days of readings and Garúa put the table on the cooperative office wall, next to the calendar, in the same pencil.
"On the ridge the two nets gave a mean of 5.2 litres per square metre per day over the ninety-six days," it said. "On the cemetery wall they gave 2.3. The two nets at each place agree with each other to within about ten per cent, so the difference between the places is not noise. The ridge is more than twice as good. Water would also run downhill from it: the ridge is 120 metres above the village. The pipe would be about 1.4 kilometres. I think it is the better site."
Marisol, who had been dreading the carrying, said nothing.
"What does it come to?" Dionisia said. She said it as she said everything, as if she were offering to pay.
Garúa did it aloud, slowly, and each line was something Dionisia could check with a pencil.
The fog comes about 150 days of the year on this coast; it had seen ninety-six and used the neighbouring weather station's record to fill in the rest, and it said that this was an assumption and that the real year could be a third more or a third less. At 5.2 litres per square metre per day, 150 days gives about 780 litres per square metre per year. A full-size net does not do as well as the standard square metre, because the wind goes round a big sheet as well as through it. It would use 0.7, and it did not know that was right.
"How big would the nets be?" Dionisia said.
"Twenty panels of twelve square metres, 240 in all. Each is six metres wide and two metres high, in a line along the ridge, 120 metres of it." It put the sum on the screen. "240 times 780 times 0.7 is 131,000 litres a year. 131 cubic metres. It is about half of the 252 you use."
"Half."
"Half, if the year is average and the 0.7 is right. If the year is a third poorer, 87 cubic metres. If a third better, 175. At the cemetery wall the same nets give 58. The tanker would still have to come, 12 times a year instead of 25, and there would have to be a cistern to carry the water you collect in the fog months over to the dry ones. I have worked it out at 30 cubic metres."
Dionisia sat very still. She did not say that half was less than she had hoped. She said, "So the ridge saves thirteen tankers a year and the wall saves six."
"Yes."
"Then it is the ridge."
"I think so. I would like you to hear from anyone who objects."
Marisol laughed, once, short. It was the laugh of a person who knows who is coming.
Eulalio Quispe was seventy-one, and he had grazed goats on the hill above the village since he was nine. The goats were a mixed flock of about sixty, and he knew them by their voices more than by their faces. He did not come to meetings. He came to this one, in his hat, and he stood at the back, and he waited until Garúa had finished before he said anything.
"Where on the ridge?"
Marisol put her finger on the map. It was a stretch of crest about 120 metres long, west of the place that everyone called the Saddle.
Eulalio did not look at the map. "That is the line of the fog," he said. "That is where it comes over. Below it there is the tara. Forty trees, perhaps. My father's goats, and his father's, ate under those trees in the dry months because the grass there stays green long after the grass on the hill is gone. You will put a net in front of the fog and the tara will be left with what is left."
"Señor Quispe," Garúa said, "that is a fair worry, and I cannot tell you that it is wrong."
Everyone in the room turned. It was not what a machine, in their experience, said.
"The nets will take water out of the air that goes through them. I can say how much. The mesh face is 240 square metres. If the fog moves at about three and a half metres a second, which is what the ridge sensor showed on the median night, and holds about 0.3 grams of liquid water in each cubic metre of air, which is a figure from the published range and not one I measured here, then on a ten-hour fog night about nine cubic metres of water go through the face of the nets. I expect them to catch about 0.9 of it, a little under one drop in ten. That fits the 0.7 I used."
It paused.
"The nine-tenths that go through are still in the air. What I do not know is how far downwind the air takes to recover. Moisture mixes in from above and from the sides. It may be ten metres. It may be several hundred. Your trees are about two hundred and fifty metres below the line, and I cannot tell you where in that range the answer falls. I would rather say so than say that you will be fine."
"And if my trees are the ones that pay?"
"Then your trees would pay for the village's water, and the village would not have asked you first."
Eulalio said nothing for a time. Dionisia, who had learned long ago that the silences in the room were worth more than the speeches, did not fill this one.
"What do you want?" he said at last. It was a plain question, put to a tablet, and it was answered plainly.
"A gap," Garúa said. "Forty metres, left open in the line, in front of your grove, so that it stays in the path of untouched fog. Sixteen panels instead of twenty, 192 square metres instead of 240. That brings the yield down to about 105 cubic metres. The tanker would come 15 times a year, not 12. The village would pay in water for the gap. And a measurement, so that we are not arguing from my guesses. Two standard collectors in your grove, a square metre each, one in the shadow of a net row and one in line with the gap. We read them every morning for a season."
"And if the one in the shadow is dry?"
"I would like us to write the rule tonight, before we have a number that anyone wants to read in their own favour. If the one behind the nets gives less than seventy per cent of what the one in the gap does, over a month of fog days, two panels come down. I chose seventy because a drop of that size is larger than the difference between two nets side by side, which was about ten per cent, so it will not be noise. If you or the cooperative think the number should be different, say so now and I will write that instead."
"Eighty," Eulalio said.
"Eighty," Garúa said. "It is more cautious for your trees. It will cost the village a bit more water in a bad month. Dionisia?"
Dionisia looked at the calendar on the wall, at the thirteen tankers a year that had become ten, and at the man in the hat who had never in his life asked this room for anything.
"Eighty," she said. "Write it in the book."
The rest was work. The pipe was laid in October by eleven people on a Saturday and a Sunday, and by the Monday the first trickle had come out at the head of the cistern, a thin grey rope of water that tasted of plastic and then of nothing.
Padre Anselmo came up from the parish on the first Sunday of November, as he did once a month, with the Mass in the back of his truck. He said it in the chapel at ten, and afterwards, because Dionisia had asked, he walked down to the cistern with the whole hamlet behind him and said a short prayer over it, and sprinkled it, and told them what he told every place he blessed a well or a roof or a boat: that water is a thing to be shared, and that the blessing is on the sharing. The children were bored. Eulalio, who had not been to Mass in six years, stood at the back with his hat in his hands.
The readings from his grove began that week. The first month of the gap, 28 fog days, the collector behind the net rows gave a mean of 3.1 litres per square metre per day and the collector in line with the gap gave 3.6. Garúa said the ratio was 86 per cent, which was above the rule and below what any of them would have liked, and that a month was a short time to be sure of anything. It wrote the figure in the book in the same pencil as the rest.
"It is eighty-six," Eulalio said.
"It is eighty-six."
"Not a hundred."
"No. The nets take some of what comes. The gap takes none. I would not tell you the difference is nothing. I would tell you it is smaller than the line you set, and that I will keep reading it."
Eulalio nodded slowly. He did not say that it was acceptable. He went up the hill to his goats.
In the second week of November the first fog of the real season came in off the sea at about four in the morning and lay on the hill, thick and cold, and Marisol walked up the ridge in the grey with a torch to read the gauges. The nets were beaded all over, each knot of the mesh holding a bright point. In the gap, where nothing was hung, the fog went through untouched and fell on the grove below.
She stood there for a moment. The water ran down the threads and into the troughs with a sound she had not been able to hear on the day she put the poles in: a small patient ticking, one drop and then the next, and under it, further down the hill, the sound of goats waking up.