\begin{table}%t2
\caption{\label{tab:h2o_line}Observed H$_2$O, H$_2^{18}$O and CH transitions\tablefootmark{a}.}
%\centering
\par
\begin{tabular}{r c c c c c c}
\hline \hline \noalign{\smallskip}
\multicolumn{1}{c}{Transition} & $\nu$ & $\lambda$   & $E_{\rm u}/k_{\rm B}$ & $A$  & Beam & $t_{\rm int}$\tablefootmark{b} \\
                               & (GHz) & ($\mu$m)    & (K)   & ($10^{-3}$ s$^{-1}$) & ($''$) & (min.) \\
\hline
H$_2$O ~~~1$_{11}$--0$_{00}$ &           1113.34 & 269.27 & \phantom{1}53.4 &           18.42 & 19 & 43.5 \\
2$_{02}$--1$_{11}$           & \phantom{1}987.93 & 303.46 & 100.8           & \phantom{1}5.84 & 22 & 23.3 \\
2$_{11}$--2$_{02}$           & \phantom{1}752.03 & 398.64 & 136.9           & \phantom{1}7.06 & 29 & 18.4 \\
3$_{12}$--3$_{03}$           &           1097.37 & 273.19 & 249.4           &           16.48 & 20 & 32.4 \\
3$_{12}$--2$_{21}$           &           1153.13 & 259.98 & 249.4           & \phantom{1}2.63 & 19 & 13.0 \\
\hline\noalign{\smallskip}
H$_2^{18}$O ~~~1$_{10}$--1$_{01}$\phantom{\tablefootmark{c}} & \phantom{1}547.68 & 547.39 & \phantom{1}60.5 & \phantom{1}3.59 & 39 & 64.3 \\
1$_{11}$--0$_{00}$\tablefootmark{c} &           1101.70 & 272.12 & \phantom{1}52.9 &           21.27 & 20 & 43.5 \\
2$_{02}$--1$_{11}$\phantom{\tablefootmark{c}} & \phantom{1}994.68 & 301.40 & 100.7 &           \phantom{1}7.05 & 22 & 46.7 \\
3$_{12}$--3$_{03}$\tablefootmark{c} &           1095.16 & 273.74 & 289.7 &                     22.12 & 20 & 32.4 \\
\hline\noalign{\smallskip}
CH\tablefootmark{d} ~~~3/2, 2$^-$--1/2, 1$^+$ & \phantom{1}536.76 & 558.52 & \phantom{1}25.8 & \phantom{1}0.66 & 39 & \\
   3/2, 1$^-$--1/2, 1$^+$ & \phantom{1}536.78 & 558.50 & \phantom{1}25.8 & \phantom{1}0.23 & 39 & \\
   3/2, 1$^-$--1/2, 0$^+$ & \phantom{1}536.80 & 558.48 & \phantom{1}25.8 & \phantom{1}0.46 & 39 &\\
\hline
\end{tabular}
\tablefoot {\tablefoottext{a}{From the JPL database of molecular spectroscopy \citep{pickett98};}
\tablefoottext{b}{total on $+$ off integration time;}
\tablefoottext{c}{observed in the same setting as the main isotopologue;}
\tablefoottext{d}{observed with H$_2^{18}$O 1$_{10}$$-$1$_{01}$.}}
\end{table}