Q400
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft
During initial descent into ZZZ from ZZZ1; the #1 HYD ISO VLV and Inboard Roll Spoilers caution lights illuminated. We then began running the #1 HYD ISO VLV E&A checklist while the Captain assumed the radios. While running the checklist; the #1 HYD QTY dropped down to 20% and slowly ran down to zero; but the HYD pressure remained adequate. We requested a hold with ATC and decided to request priority handling. When the caution lights extinguished; we then ran the #1 HYD QTY LOW Checklist in the E&A checklist. Once all checklists were completed and all parties were informed; we then proceeded to ZZZ to land. We opened up the Flap Power caution checklist in case our flaps did not extend. We made sure to configure early; in case the flaps did not deploy; and because the flaps were going to operate slower than usual. We were able to land without incident; and taxi to the gate with minimal normal breaking and the use of the emergency break. We had crash fire rescue and a tug standing by in case we needed any assistance.  As stated in event narrative.
Q400 First Officer reported loss of Hydraulic System 1 Fluid Quantity resulted in a precautionary landing.