Groundwater from a municipal utility district is less expensive than surface water (because of the added treatment and delivery systems). However, that's not the only cost:
If you use groundwater and cause subsidence, you may cause additional flooding and need to get flood insurance at ~$500/year. If you use ~10,000 gallons a month that's equal to and additional $4 per 1000 gallons fee on your groundwater bill, essentially the same as the surface water bill.
However, that 's not all!
If you do get flooded because of the additional subsidence, you'll have to pay the deductible on the home repairs. Typical deductibles are $5000 so that's an additional out of pocket expense because of subsidence, or about another $0.83/1000 gallons on your groundwater bill over the next 50 years.
However, that's not all!
If the county has to modify flood drainage because of additional subsidence that will be an additional cost to county residents. Right now the regional flood planning group estimates we'll need to spend $1 billion over the next 50 years because of additional development and higher rainfall, NOT SUBSIDENCE. Assuming another 50% of flood projects for subsidence would be another $0.14/1000 gallons on your groundwater bill over the next 50 years.
So your actual cost of using groundwater needs to include flood insurance, deductible payment and additional taxes, in addition to the cost of the water.
Or, you can use surface water, at a lower overall cost.