Thank you for the information about Japan. How are the small drainage/irrigation channels tagged currently in Japan?
Are most tagged as waterway=drain, waterway=canal or waterway=ditch? We have lots of these in Indonesia, in the rice-growing areas with irrigated fields, but most are more like deep ditches, dug directly into the ground and unlined. Only the larger ones have been lined with stone or concrete. > the California aquaduct is huge and manages the supply for California It's tagged as a waterway=canal over most of it's stretch, and I believe this is correct: https://www.openstreetmap.org/search?query=%22California%20Aqueduct%22#map=7/36.344/-120.167 There are a couple short sections of pipeline where the water is pumped uphill as well. > Adding purpose via an additional tag is the only way to make sense of it. > (and "both waste and irrigation" must be an option). We could consider a tag like "usage=drainage", in addition to "usage=irrigation" This could be combined as "usage=irrigation;drainage"? Joseph On 5/30/19, John Willis via Tagging <tagging@openstreetmap.org> wrote: > > > Javbw > >> On May 29, 2019, at 10:37 AM, Joseph Eisenberg >> <joseph.eisenb...@gmail.com> wrote: >> >> What, then, should be the distinguishing characteristic between >> waterway=canal and waterway=ditch or =drain? Width or importance or >> navigability, or should we still mention the usage as the main >> difference? > > The biggest issue - by far - is conflating construction with purpose. This > makes the tags ambiguous. We can invent a definition, but the ambiguity will > remain because of our tag value choices, as we have to be careful to manage > "purpose". > > Canal implies construction and purposes. (Many varying purposes). > > Drain implies a purpose > > Ditch implies construction. > > Canals move things from place to place. aquaducts usually exist to move > water from one large water body (a lake or river) to another (a holding lake > or another river). They are very large (no less than 1 meter, perhaps, > usually more) > > Drains take away waste. We have added "construction" to the definition: > "they are lined - concrete or steel or whatever" > > Ditches are dug into existing ground. > > In some places, irrigation is separate from storm water management. A storm > drain takes wastewater to a river. An irrigation ditch moves water from a > supply to a field for orange trees to soak it up. These simple definions > work well enough for Southern Califorina. > > But the Purpose becomes muddied in some places when they are linked > together. Here in Japan, we probably have 4x the length of drains than > roads. It is immense. They are in every street and and every rural area. > They channel rainwater across the land for farming. The "storm drain" system > is the irrigation system. One Field's runnoff is the next Field's supply. > Drains run from small weirs in streams and canals. These cast concrete > drains surround each group of fields. The drains feed ditches which flood > the fields and *go back* into the same drains which *feed* the next set of > ditches. They are cross connected everywhere, like a spiderweb. Farmers turn > them off with large sluices, little sliding gates, and dirt mounds to > control how and when fields flood. They have thousands of tiny resivoirs the > size of a backyard pool scattered everywhere. The help collect rain and > balance distribution load for irrigation. > > Irrigation canals - aquaducts - are quite rare. Every town has one or two. > They move water from one water body to the next, balancing the supply in an > area (the California aquaduct is huge and manages the supply for > California), but only one aquaduct I Know of is larger than 1 meter). > > Drains collect and/or distribute water in man-made structures to/from larger > ones (rivers, streams, lakes etc) > > Ditches collect and/or distribute water in ditches carved into the ground, > with little to no improvement. > > Adding purpose via an additional tag (like canal does) is the only way to > make sense of it. (and "both waste and irrigation" must be an option). > > Javbw > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging > _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
