Narrative:

While cruising at FL380 we noticed the a side engine driven hydraulic pump low pressure light illuminate intermittently. We pulled out the QRH to review procedures when the light illuminated steady. We completed QRH procedures and noticed the a side fluid level at 18%. Pressure was normal at 3030 [psi]. We then began to review the QRH procedure for a system loss. At this point we noticed level continuing to drop. We notified dispatch via ACARS and after a few minutes dispatch recommended diversion to [a nearby alternate]. We concurred and notified ATC of our intention. We then notified the flight attendants of our plan and instructed them to begin securing the cabin. We then notified the passengers. Since we did not completely lose the system; we were able to lower the gear normally. We informed ATC [of our runway preference]. They informed us that [coordination would need to be made] to be able to use that runway. [ATC was advised] and we landed without incident; taxied off the runway and were inspected by crash fire rescue equipment. We were then released by crash fire rescue equipment to taxi to the gate where the logbook was filled out and maintenance notified. Passengers completely understood as we switched aircraft and eventually departed uneventfully. First officer and crew performed flawlessly.

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Original NASA ASRS Text

Title: B737-700 Captain reported diverting to an alternate airport after fluid loss in the 'A' hydraulic system.

Narrative: While cruising at FL380 we noticed the A Side Engine Driven Hydraulic Pump Low Pressure light illuminate intermittently. We pulled out the QRH to review procedures when the light illuminated steady. We completed QRH procedures and noticed the A side fluid level at 18%. Pressure was normal at 3030 [psi]. We then began to review the QRH procedure for A System Loss. At this point we noticed level continuing to drop. We notified Dispatch via ACARS and after a few minutes Dispatch recommended diversion to [a nearby alternate]. We concurred and notified ATC of our intention. We then notified the Flight Attendants of our plan and instructed them to begin securing the cabin. We then notified the passengers. Since we did not completely lose the system; we were able to lower the gear normally. We informed ATC [of our runway preference]. They informed us that [coordination would need to be made] to be able to use that runway. [ATC was advised] and we landed without incident; taxied off the runway and were inspected by CFR. We were then released by CFR to taxi to the gate where the logbook was filled out and Maintenance notified. Passengers completely understood as we switched aircraft and eventually departed uneventfully. FO and Crew performed flawlessly.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.