Annual Precipitation in Texas
y. zhang
03-28-2017
Obtain the raw data
The annual precipitation data for Texas is available from the Texas Water Development Board.
- The data is distributed in multiple data files in ASCII format.
- Each data file is for a quadrangle area in Texas.
- There are 92 quadrangles cover the entire Texas. Some major cities such as Austin is in the quadrangle 710, Houston in 812, San Antonio in 809 and Dallas in 511.
Download the raw data
The data file url is http://midgewater.twdb.texas.gov/evaporation/quadrangle/XXX/precipitation-tabular.txt, where XXX is the quadrangle number, therefore we can loop all possible numbers to download all data files.
quadrangleno=c(104:108,204:208,304:309,404:414,
504:514,601:614,701:714,803:814,907:912,1008:1011,1108:1110,1210)
url1 <- "http://midgewater.twdb.texas.gov/evaporation/quadrangle/"
url2 <- "/precipitation-tabular.txt"
url <- paste(url1,quadrangleno,url2,sep="")
destfile <-paste("./tx_precipitation_data/",quadrangleno,"_data.txt",sep="")
for (i in 1:length(url))
download.file(url[i],destfile=destfile[i])
library(ggplot2)
library(reshape2)
library(dplyr)
datafile <- "./tx_precipitation_data/texas_prcipitation_1940-2015.txt"
pd <- read.table(datafile,header=T,comment.char="",check.names=F)
names(pd)[1] <- "QUAD"
pd_all <- aggregate(pd$ANNUAL,by=list(YEAR=pd$YEAR),mean)
colnames(pd_all)[2] <- "ANNUAL"
pd_all <- mutate(pd_all,QUAD=9999L)
pd_all <- merge(pd,pd_all,all=T)
Data processing and plot
region <- data.frame(name=c("Austin","Houston","San Antonio","Dallas","TX"),
quad=c(710,812,809,511,9999))
sq <- c(710,812,9999)
pd1 <- subset(pd_all[,c("QUAD","YEAR","ANNUAL"),drop=F], QUAD %in% sq)
pd2 <- mutate(pd1,location=region$name[match(pd1$QUAD, region$quad)])
pd_long <- melt(pd2, id=c("YEAR","QUAD","location") )
g <- ggplot(pd_long,aes(y=value,x=YEAR,colour=location))+geom_line()
g <- g+xlab("Years")+ylab("Annual Precipitation (unit: inch)")
g <- g+theme(axis.text=element_text(size=12), axis.title=element_text(size=14),
legend.title=element_text(size=14), legend.text=element_text(size=12))
g <- g+xlim(1945,2015)
g <- g+geom_smooth(se=F)
Plot the selected precipitation
- The annual precipitation from 1940 to 2015 for the region near Austin, Houston and the entire Texas
