I am examining the use of underground pipe network information in the prediction of soil moisture in metropolitan areas; drinking water pipes leak water to the surrounding soil, storm sewer and wastewater pipes receive water from the surrounding soil. I am assuming certain leakage rates based on the size and age of the pipes - older pipes leak/receive more, larger pipes leak/receive more. I am missing information for certain pipes on their age and size.
Because this is a first pass at building a working model (set of mathematical equations predicting soil moisture), I don't need the model to be perfect - but I do need to replace my NODATA values with some estimate of age and size.
What is the best method for replacing my NODATA values? With the mean, median, or a random set of values that follow the distribution of the original data?
Total number of pipes: 10779, with 1034 = NODATA. Age range: 1858 - 1992.