First, install the Intel Fortran Compiler.

You can download the incomplete source code of PeakFQ from its website. Here, I'll use PeakFQ_7.5.1.src.zip.

compile_peakfq.sh

#!/bin/sh
 
# download source code
wget https://water.usgs.gov/software/PeakFQ/code/7.5.1/PeakFQ_7.5.1.src.zip
 
# unzip it
mkdir -p ~/usr/local/src
unzip PeakFQ_7.5.1.src.zip -d ~/usr/local/src
cd ~/usr/local/src
mv PeakFQ_7.5.1.src/src/FORTRAN peakfq
rm -rf PeakFQ_7.5.1.src
cd peakfq
 
# rename all filenames to lowercase
for i in *.*; do
  j=$(echo $i | tr A-Z a-z)
  [ $i = $j ] || mv $i $j
done
 
# rename include and module names in source files to lowercase
for i in *.*; do
  grep -q ".*.INC'" $i || continue
  for j in $(grep ".*.INC'" $i | sort -u | fromdos | sed "s/^[^']*'\|'$//g"); do
    k=$(echo $j | tr A-Z a-z)
    sed -i "s/$j/$k/" $i
  done
done
 
# move DENYNONE from ACTION to SHARE
sed -Ei "s/(, )(DENYNONE)/'\1SHARE='\2/" wdoppc90.for
 
# comment out non-existent modules and data type
sed -Ei 's/^(.*(KERNEL32|T_OVERLAPPED))/!\1/' scenmod.f90
 
# comment out Windows functions
sed -Ei 's/^(.*(PeekNamedPipe|ReadFile|WriteFile))/!\1/' scenmod.f90
 
# fix disclaimer line
sed -i "/^ *WRITE(DISCLM(1)/a \        DISCLM(2) = ''\r" j407xe.for
 
# download missing files
for i in \
  adwdm/cfbuff.inc \
  adwdm/cdrloc.inc \
  adwdm/fmsgwd.inc \
  adwdm/utwdmd.for \
  adwdm/utwdmf.for \
  adwdm/utwdt1.for \
  adwdm/wdatm1.for \
  adwdm/wdmchk.for \
  adwdm/wdmess.for \
  wdm/ctsbuf.inc \
  wdm/cwdmid.inc \
  wdm/cwtsds.inc \
  wdm/tsbufr.for \
  wdm/wdatm2.for \
  wdm/wdatrb.for \
  wdm/wdatru.for \
  wdm/wdbtch.for \
  wdm/wdmid.for \
  wdm/wdtms1.for \
  wdm/wdtms2.for \
  ; do
  wget https://svn.oss.deltares.nl/repos/openda/trunk/model_hspf/fortran/libanne4.0/src/$i
done
 
# create main.f90
cat << 'EOT' > main.f90
character(len=256) :: specfile
 
if(command_argument_count().eq.0) then
  write(*,*) "Usage: peakfq specfile"
else
  call get_command_argument(1, specfile)
  call peakfq(specfile)
endif
end
EOT
 
# create Makefile
cat << 'EOT' > Makefile
FC=ifx
LDFLAGS=-nofor-main
 
all: peakfq
 
clean:
	$(RM) *.o EMAUtil/*.o *.mod peakfq
 
peakfq: \
	main.o \
	EMAUtil/dcdflib1.o \
	EMAUtil/imslfake.o \
	EMAUtil/probfun.o \
	compspecs.o \
	datsys90.o \
	emafit.o \
	emathresh.o \
	j407wc.o \
	j407xe.o \
	ktutil.o \
	peakfq.o \
	pkfqsta.o \
	pkwdm.o \
	qfdprs.o \
	scenmod.o \
	stationdata.o \
	stgaus.o \
	stutil.o \
	tsbufr.o \
	utchar.o \
	utcpgn.o \
	utdate.o \
	utgnrl.o \
	utj407.o \
	utnumb.o \
	utstat.o \
	utwdmd.o \
	utwdmf.o \
	utwdt1.o \
	wdatm1.o \
	wdatm2.o \
	wdatrb.o \
	wdatru.o \
	wdbtch.o \
	wdmchk.o \
	wdmess.o \
	wdmid.o \
	wdoppc90.o \
	wdpeak.o \
	wdtble.o \
	wdtms1.o \
	wdtms2.o
	$(FC) $(LDFLAGS) -o $@ $^
 
peakfq.o: emathresh.o compspecs.o
 
pkfqsta.o: scenmod.o
 
j407xe.o: emathresh.o stationdata.o
 
j407wc.o: emathresh.o
 
%.o: %.f90
	$(FC) $(FFLAGS) -c -o $@ $<
 
%.o: %.for
	$(FC) $(FFLAGS) -c -o $@ $<
EOT
 
# build
make
 
# install PeakFQ for Windows; find and copy pkfqms.wdm in lowercase
# download it from this website
wget https://clawiki.isnew.info/_media/howtos/pkfqms.wdm

You don't need to run this command, but I used it to find undefined references:

# see what symbols are undefined
for i in $(make &> /dev/stdout | grep "undefined reference" | sed 's/.*`//; s/_.*//' | sort -u); do
  if ! grep -qiE "(function|subroutine) *$i" *.* */*.*; then
    echo "$i: NOT FOUND"
  fi
done