CRJ-200 Captain reported a hydraulic malfunction during cruise flight. The Captain diverted to an alternate airport; landed safely; then needed to be towed to the ramp.

Narrative

On Day 0 the Second in Command (SIC) for this flight and I were flying from ZZZ back up to ZZZ1. During the cruise flight at Flight level 310; I noticed that the hydraulic level in flight was down to 35% which made it a white indication on the synoptic page. I took note of this original indication at XA:42 pm and brought it to my Co-Pilot's attention. 5 minutes later the level dropped to 30% and then we also lost 100 PSI from the hydraulic system 3 at that point as well. At this point; we realized there was a leak somewhere in the system; and needed to go to the nearest suitable airport. At XA:53pm it was down to 20% then at XB:03 pm it was at 10%. The SIC and I [requested priority] with the ZZZ center. They passed us to approach. Then shortly after we received the HYD 3 LO PRESS Message on the EICAS screen. This QRH procedure once completed tells you to land at the nearest suitable airport; for us this was ZZZ2. The Co-Pilot read me the QRH procedure and we accomplished all the necessary items to successfully lower the landing gear manually with the emergency landing gear extension handle. Once the checklist was completed and we confirmed the gear was down and locked on the EICAS screen we prepared for landing. We landed the aircraft on the runway safely and once we were at a slow enough speed we were able to taxi the aircraft off the runway onto a taxiway to avoid closing the runway for other arrivals at ZZZ2. There was no damage done to the aircraft and no crew or passengers had any injuries. Airport operations then got a tug and moved us over to the ramp where we then de-planned the passengers.2 days later we were notified by the mechanics that our 3A hydraulic pump had failed. That was the reason we lost the quantity so fast in Hydraulic System 3. I learned a lot from this situation and I believe our Crew handled this situation with professionalism and poise. I'm very thankful to air traffic control and airport operations for helping us so much with getting us to the closest airport safely and efficiently.