Regional Jet 700 ER/LR (CRJ700)
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Procedure; Software and Automation; Aircraft
As we taxied out to our assigned runway of XXL in ZZZ; we received several EFIS COMP MON [airspeed disagree] caution messages. They would only stay on for a few seconds; then disappear as I would reset the master caution that would accompany the ding. Once we were cleared to 'line up and wait' on our assigned runway of XXL I taxied on the runway; and handed the controls to the First Officer (FO) and we waited for our takeoff clearance. A few moments later; we were cleared to takeoff with clearance of 'RNAV to ZZZZZ Runway XXL; cleared for takeoff.'  The First Officer then initiated the take off sequence. As she pushed the thrust levers forward and we started to move down the runway; yet another EFIS [Electronic Flight instrument System] COMP MON caution came on with an associated ding and master caution warning. I looked to ED1 (primary EICAS) to find the caution and said aloud 'continue.' and the The First Officer continued with the takeoff roll. As soon as I looked back at the airspeed indicator tape; I saw we already were at V1 speed; and Vr speed. So I said aloud 'V1; rotate' as soon as we rotated the STALL FAIL caution illuminated on ED1. The stick shaker activated shortly thereafter; followed by a warbling tone to indicated a stall had happened. I look at my airspeed indication 'tape' and now saw both red 'barber pole' indicators starting to come together. As I saw this; I quickly looked at the FO airspeed indication and back at the backup airspeed indication. I noticed they both were reading the same thing and said aloud; 'looks like we have a stall fail caution; and my airspeed is showing incorrect indications.' I then began to run the QRC and QRH for the stall fail and loss of reliable airspeed indications. After running the QRH; we promptly returned to ZZZ without incident and taxied to a gate.  According to Maintenance; water entered into the left-side pitot tube and caused an erroneous airspeed error; and potential STALL FAIL caution.
Flight Crew did an Air Tun Back after the aircraft Electronic Flight instrument System computer failed and they lost all air data.