[R] Question regarding reservoir volume and water level
peter dalgaard
pd@|gd @end|ng |rom gm@||@com
Tue Apr 9 16:01:50 CEST 2024
So, you know how to get volume for given water level.
For the reverse problem, you get in trouble because of the nonlinearity inherent in the dependence of surface area on the level.
I don't think there is a simple solution to this, save for mapping out the volume as a function of water level and solving equations for the water level using (say) uniroot(). Which may actually suffice for practical purposes.
For small changes, finding the derivative of the relation is easy: d(volume) = Area * d(level) and this can be used as an approximate relation as long as the Area remains nearly constant.
However generic questions like doubling the volume are impossible to answer without knowledge of the reservoir shape. E.g. in a cylindrical reservoir halving the water level also halves the volume, but in a conical reservoir, halving the level leaves only 1/8 of the volume.
-pd
> On 8 Apr 2024, at 05:55 , javad bayat <j.bayat194 using gmail.com> wrote:
>
> Dear all;
> Many thanks for your replies. This was not homework. I apologize.
> Let me explain more.
> There is a dam constructed in a valley with the highest elevation of 1255
> m. The area of its reservoir can be calculated by drawing a polygon around
> the water and it is known.
> I have the Digital Elevation Model (DEM) of the region (reservoir and its
> surrounding area). I have calculated the volume of the current reservoir
> (7e6 m3) using the following codes.
> library(raster)
> library(terra)
> library(exactextractr)
> library(dplyr)
> library(sf)
> # Calculate volume for polygon
> # Read the DEM raster file
> r <- rast("E:/...DEM.tif")
> # Read the polygon shapefile
> p <- st_read("E:/...Dam.shp")
>
> r <- crop(r, extent(p))
> r <- mask(r, p)
>
> # Extract the cells in each polygon and calculate the area of each cell
> x <- exact_extract(r, p, coverage_area = TRUE)
> # Extract polygon values as a dataframe
> x1 = as.data.frame(x[1])
> head(x1)
> x1 = na.omit(x1)
> # Calculate the height above the minimum elevation in the polygon
> x1$Height = max(x1[,1]) - x1[,1]
> # Calculate the volume of each cell
> x1$Vol = x1[,2] * x1[,3]
> sum(x1$Vol)
> x2 = x1[,c(1,2,4)]
> x2 = sort(x2,'value')
> head(x2)
> x3 <- aggregate(Vol ~ value, data = x2, FUN = sum)
> x4 <- aggregate(coverage_area ~ value, data = x2, FUN = sum)
> x5 = cbind(x3, Area = x4[,2])
> library(dplyr)
> x6 <- x5 %>%
> mutate(V_sum = cumsum(Vol)) %>%
> mutate(A_sum = cumsum(Area))
> plot(x6$value~x6$V_sum)
>
> And I thought that it is possible to get the elevation for a specific
> volume by linear model between elevation and volume, as follow:
>
> # Get a linear model between elevation and the volume
> lm1 <- lm(value ~ V_sum, data = x6)
> d <- data.frame(V_sum = 14e6) #
> predict(lm1, newdata = d)
>
> But it is not possible through the LM.
> Now I want to know what would be the water level in the reservoir if the
> reservoir volume doubled or we adding a known volume to it?
> Also what would be the volume if the water level increases to 1250 m?
>
> I would be more than happy if you help me to do this.
> Sincerely
>
> On Mon, Apr 8, 2024 at 12:23 AM <avi.e.gross using gmail.com> wrote:
>
>> John,
>>
>> Your reaction was what my original reaction was until I realized I had to
>> find out what a DEM file was and that contains enough of the kind of
>> depth-dimension data you describe albeit what may be a very irregular cross
>> section to calculate for areas and thence volumes.
>>
>> If I read it correctly, this can be a very real-world problem worthy of a
>> solution, such as in places like California where they had a tad more rain
>> than usual and some reservoirs may overflow. Someone else provided what
>> sounds like a mathematical algorithm but my guess is what is needed here is
>> perhaps less analytic since there may be no trivial way to create formulas
>> and take integrals and so on, but simply an approximate way to calculate
>> incremental volumes for each horizontal "slice" and keep adding or
>> subtracting them till you reach a target and then read off another variable
>> at that point such as depth.
>>
>> Some care must be taken as water level has to be relative to something and
>> many natural reservoirs have no unique bottom level. Some water may also be
>> stored underground and to the side and pour in if the level lowers or can
>> be
>> used to escape if the level rises.
>>
>>
>> -----Original Message-----
>> From: R-help <r-help-bounces using r-project.org> On Behalf Of Sorkin, John
>> Sent: Sunday, April 7, 2024 3:08 PM
>> To: Rui Barradas <ruipbarradas using sapo.pt>; javad bayat <j.bayat194 using gmail.com
>>> ;
>> R-help <R-help using r-project.org>
>> Subject: Re: [R] Question regarding reservoir volume and water level
>>
>> Aside from the fact that the original question might well be a class
>> exercise (or homework), the question is unanswerable given the data given
>> by
>> the original poster. One needs to know the dimensions of the reservoir,
>> above and below the current waterline. Are the sides, above and below the
>> waterline smooth? Is the region currently above the waterline that can
>> store
>> water a mirror image of the region below the waterline? Is the region above
>> the reservoir include a flood plane? Will the additional water go into the
>> flood plane?
>>
>> The lack of required detail in the question posed by the original poster
>> suggests that there are strong assumptions, assumptions that typically
>> would
>> be made in a class-room example or exercise.
>>
>> John
>>
>> John David Sorkin M.D., Ph.D.
>> Professor of Medicine, University of Maryland School of Medicine;
>> Associate Director for Biostatistics and Informatics, Baltimore VA Medical
>> Center Geriatrics Research, Education, and Clinical Center;
>> PI Biostatistics and Informatics Core, University of Maryland School of
>> Medicine Claude D. Pepper Older Americans Independence Center;
>> Senior Statistician University of Maryland Center for Vascular Research;
>>
>> Division of Gerontology and Paliative Care,
>> 10 North Greene Street
>> GRECC (BT/18/GR)
>> Baltimore, MD 21201-1524
>> Cell phone 443-418-5382
>>
>>
>>
>>
>> ________________________________________
>> From: R-help <r-help-bounces using r-project.org> on behalf of Rui Barradas
>> <ruipbarradas using sapo.pt>
>> Sent: Sunday, April 7, 2024 10:53 AM
>> To: javad bayat; R-help
>> Subject: Re: [R] Question regarding reservoir volume and water level
>>
>> Às 13:27 de 07/04/2024, javad bayat escreveu:
>>> Dear all;
>>> I have a question about the water level of a reservoir, when the volume
>>> changed or doubled.
>>> There is a DEM file with the highest elevation 1267 m. The lowest
>> elevation
>>> is 1230 m. The current volume of the reservoir is 7,000,000 m3 at 1240 m.
>>> Now I want to know what would be the water level if the volume rises to
>>> 1250 m? or what would be the water level if the volume doubled
>> (14,000,000
>>> m3)?
>>>
>>> Is there any way to write codes to do this in R?
>>> I would be more than happy if anyone could help me.
>>> Sincerely
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>> Hello,
>>
>> This is a simple rule of three.
>> If you know the level l the argument doesn't need to be named but if you
>> know the volume v then it must be named.
>>
>>
>> water_level <- function(l, v, level = 1240, volume = 7e6) {
>> if(missing(v)) {
>> volume * l / level
>> } else level * v / volume
>> }
>>
>> lev <- 1250
>> vol <- 14e6
>>
>> water_level(l = lev)
>> #> [1] 7056452
>> water_level(v = vol)
>> #> [1] 2480
>>
>>
>> Hope this helps,
>>
>> Rui Barradas
>>
>>
>> --
>> Este e-mail foi analisado pelo software antivírus AVG para verificar a
>> presença de vírus.
>> http://www.avg.com/
>>
>> ______________________________________________
>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.r-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>> ______________________________________________
>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>
> --
> Best Regards
> Javad Bayat
> M.Sc. Environment Engineering
> Alternative Mail: bayat194 using yahoo.com
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes using cbs.dk Priv: PDalgd using gmail.com
More information about the R-help
mailing list