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THC, the main psychoactive component of cannabis, may only be detectable in saliva and oral fluid for 2–24 hours in most cases. [8] [9] The main metabolite excreted in the urine is 11-Nor-9-carboxy-THC, also known as THC-COOH. Most cannabis drug tests yield a positive result when the concentration of THC-COOH in urine exceeds 50 ng/mL. [10]
This is a list of free and open-source software for geological data handling and interpretation. The list is split into broad categories, depending on the intended use of the software and its scope of functionality. Notice that 'free and open-source' requires that the source code is available and users are given a free software license.
The first routine measurements of river flow in England began on the Thames and Lea in the 1880s, [2] and in Scotland on the River Garry in 1913. [3] The national gauging station network was established in its current form by the early 1970s and consists of approximately 1500 flow measurement stations supplemented by a variable number of temporary monitoring sites. [2]
In hydrology, a rating curve is a graph of discharge versus stage for a given point on a stream, usually at gauging stations, where the stream discharge is measured across the stream channel with a flow meter. [1] Numerous measurements of stream discharge are made over a range of stream stages.
For free flow, the equation to determine the flow rate is simply Q = CH a n where: Q is flowing rate (ft 3 /s) C is the free-flow coefficient for the flume (see Table 1 below) H a is the head at the primary point of measurement (ft) (See Figure 1 above) n varies with flume size (see Table 1 below) Parshall flume discharge table for free flow ...
A stream hydrograph is commonly determining the influence of different hydrologic processes on discharge from the subject catchment. Because the timing, magnitude, and duration of groundwater return flow differs so greatly from that of direct runoff, separating and understanding the influence of these distinct processes is key to analyzing and simulating the likely hydrologic effects of ...
[30] [31] In recent years, budget constraints have forced the USGS to rely on donations of time by civilian volunteers in an attempt to update its 7.5-minute topographic map series, and USGS stated outright in 2000 that the program was to be phased out in favor of The National Map [32] (not to be confused with the National Atlas of the United ...
Mounted sideways on a wall or bridge piling in rivers or canals, it can measure the current profile from bank to bank. In very deep water they can be lowered on cables from the surface. The primary usage is for oceanography. [4] The instruments can also be used in rivers and canals to continuously measure the discharge.