This isn’t a rant. We who like water to drink and for other reasons have a fundamental problem. It needs fixing and a way to start doing that is to stop using the word "watershed" for everything about "land."
I’ve discussed in a few previous blogs the “platform” as a mappable area with its volume where people can, within limits, exercise their ideas and decisions. It is not pre-ordained. It just is and with enough time and resources can be vastly changed. That forests or cropland may exist now is seen as a decision. The platform is assumed to be “the blank slate” and ready for action or inaction based on decisions to be made by managers.
I bothered several mined-land reclamation people when I claimed that I could grow bananas on strip mined areas. (Their minds were on seeds and trees and “natural” reclamation and minimum expenditures, not on possibilities within plastic greenhouses, etc. or profits.) Wildlife people typically think of natural means to increase populations as the only major techniques appropriate.
“Watersheds” has similarly trapped thought. There are viewsheds, sound- and noise-sheds, and watersheds. Maybe there should be fishsheds, molluscsheds, or cornsheds. “Sheds” are mapped areas that name one but aggregate many phenomena about such areas.
Watersheds were first mapped for one purpose such as for estimating the water that runs off of an area (for commercial uses or flood risks). Other people then use the mapped areas for their purposes, compromising their objectives for the seeming inconsequential map differences that occur between their desired map and the one in hand. Caught up by some possibilities, people have propounded the usefulness of watersheds for natural resource management, county planning, and wildlife resource management city planning, etc.
Groundwater source is a notable example of such compromise and errors for watersheds. All water that falls on one area may not be stored or may not emerge within the same area. Human populations do not separate well into watersheds. Stream fish high in a watershed may not be the same species as those in lower water reaches. Few animals or plants are watershed specific. They ignore the crest boundary line, one that is more easily marked on maps than in the field.
The same rainfall per unit area within a so-called watershed can have different results in a stream when a forested band occurs above or below a grassed rangeland within that mapped area. We know that even for small watersheds there is not uniform runoff, percolation, evaporation, or transpiration. Assuming equality is known to be wrong; to do so is not ignorance.
The triangular area on a map between typically-mapped boundaries (as shown here) is rarely discussed or analyzed and does not fit conventional definitions of watersheds. (Surface flows (the arrows with B's) violate the single common water collection point of many definitions.)
I am of the "glass half empty" school. I do not think that there have been major advances and improvements in the acceptance and demonstrated use of the research findings or the active use of the watershed concept in planning. There are some exceptional projects, but these do not deny the observation about hundreds of them. Conventional watershed management promotion and practice have not worked (as judged by many criteria). Improvements and an alternative are needed. I propose that watershed analysis be limited to the analysis of the water budget within an area.
For faunally-related work and more rural resource management we need to use alpha units, 10 meter by 10 meter sections or cells of a map grid.
Such use can reduce the high variances we discover, deduce the totaling and averaging done in traditional watershed studies, allow us to re-consider and analyze the triangular areas, and include fog drip.
Fog drip is the moisture accumulated by trees and shrubs from fog and cloud cover, that combed from the air. It is conspicuous as hoarfrost but that is rare in many areas. It is poorly or rarely accounted (by rain gages) and may be as much as 5-10% of the total precipitation reported for some areas. It’s enough to cause a little variance in runoff-equations that depend upon estimates of storage, precipitation, evaporation and transpiration of plants.
We need to include improved surface-storage measures, revise snow water equivalents based on evaporation models, and revise and revive our knowledge of the sequence of weather events and runoff and water infiltration. (The amount of rainfall that runs off of soils differs greatly but not as much as among differences that occur when soil is frozen or not or when dry or recently made wet by rain. We need to include nearness. We can estimate and control for these factors by using alpha units … previously impossible or grossly unimaginable for entire watersheds.)
Each such watershed is unique for it is composed of unique entities. Averaging all of the factors, then assuming that everything within a boundary is the same average value seems unwise. To aggregate is to lose data and the ability to transform it into several ecologically or economically relevant values. We can keep data separate as long as possible within the computer, then use models to synthesize factors into key decision alternatives about optimum restoration, uses, protections, and future potentials. Why should we average and aggregate and group knowledge when we know every North-facing slope performs very differently than the South-facing slope of a typical watershed. The watershed-oriented effort gives us no advantages, limits some work (groundwater analyses and management), ads to some work (plant and animal species analyses), adds extraneous information to some work (e.g., wide-ranging wild animals or animals with very narrow ranges and most fossil-fuel extraction analyses), and prevents us thinking about the unique spots of the land being managed, each such alpha unit having 100+ known factors stored that are only very peripherally linked (or linkable) to costly-gotten information about the watershed.
We do need to improve knowledge of water systems but not constrain analyses or planning to thinking within the boundary. One word, "watershed,” can have many meanings and so can the word “management.” Together they are blatantly for political applications or in need of abolition for future work on the serious problems facing land and water management for us all.
Crescent management could become the replacement concept for any mapped land or water platform (e.g., a map “window,” circular working area, designated ownership(s)) and its associated above or below-surface volumes.