the activity of a comet. It can be measured directly from near-infrared observations or derived from OH emission at 3090 Å  and radio wavelengths or from H Lyman-$\alpha$ emission at 1216 $\AA$ [@Combi1986] assuming that both OH and H arise from the dissociation of H$_2$O. In this work, we computed the vectorial-equivalent water production rates according to an empirical procedure based on a comparison of OH and water production rates derived from the mean lifetimes, velocities, and scale lengths given by [@Cochran1993]. [@Schleicher1998] built an empirical relationship $Q(H_2O)=1.361 r_h^{-0.5} Q(OH)$ based on a r$_h^{-0.5}$ dependence of the H$_2$O outflow velocity, a photodissociation branching ratio for water to OH of 90%, and the heliocentric distance. Figure \[fig:rate\_H2O\] shows the water production we derived compared to previous apparitions (with different techniques) as a function of days to perihelion. We used the formula given above to convert Q(OH) to water production rates for [@Schleicher2018] data. [@Combi2011] derived the production rates from the H Ly-$\alpha$ emission observed by the SWAN instrument on board SOHO in 1998 and in 2005. [@Combi1992] values are derived from H Ly-$\alpha$ emission observed by the IUE mission for the 1985 apparition. From the Pioneer Venus Orbiter ultraviolet system (UVS) 