B727 DEP TO THE N FROM RNO ACTIVATES THE ATC LOW ALT WARNING SYS AND GPWS ON ACFT. CREW STATES THAT ACFT WAS JUST UNDER GROSS WT ALLOWABLE WITH A WARM TEMP. THEIR SCENARIO WAS LESSENED BY THE FACT THAT THEIR ACR HAS A 360 DEG HDG FOR CLB. THE PUBLISHED 330 DEG HDG WOULD BE MORE DANGEROUS.

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DEPARTING RENO ARPT (WX 110 FT SCATTERED; MORE THAN 10 MI VISIBILITY; CALM WINDS TEMP 24 DEGS C) RWY 34L. TKOF (ACARS) NUMBERS SHOWED 129 PAX. AFTER TKOF ON TWR ASSIGNED HEADING (AS PER OUR ACR'S OPS REQUIREMENT) 360 DEGS. APPROX 3-5 MI N OF RENO RECEIVED BOTH A GPWS TERRAIN WARNING AND TWR CALLED WITH LOW ALT WARNING. AS WE HAD THE TERRAIN IN SIGHT AND KNEW WE WOULD CLR IT; WE DIDN'T NEED TO OVERBOOST THE ENGS OR TAKE EVASIVE MANEUVERS. MY CONCERN IS FOR FUTURE ACFT FLYING OUT OF RENO. ATC DEP PROCS CALL FOR A 330 DEG HDG (WHICH WE WERE ORIGINALLY ASSIGNED BUT OUR OPS AT OUR ACR MANDATE 360 DEGS FROM MM); THE 330 DEG HDG WOULD HAVE COMPOUNDED THE PROB; BECAUSE THE TERRAIN IS HIGHER TO THE NW. THE SECOND PROB IS THAT AFTER TKOF; REVISED PAX TOTALS SENT VIA COMPUTER (AFTER TKOF) SHOWED A REVISED LOAD OF 132 PAX VERSUS 129 PAX ORIGINALLY. WE WERE STILL UNDER OUR TKOF GROSS WT BY 1200 LBS. WHAT IDENTED THIS ERROR; WAS A REQUIRED PAX COUNT AS PER FLT OPS MANUAL BEFORE TKOF. GIVEN A SCENARIO OF A DIFFERENT CARRIER; IN BAD WX; HOT DAY ON A 330 DEG HDG THIS DEP COULD TURN OUT FATAL. THIS IS AN EXAMPLE OF NOISE ABATEMENT PROCS REQUIRING GREATER VERT CLB AND (SHOULD AN ENG FAIL) POSSIBLY JEOPARDIZING SAFETY. SUPPLEMENTAL INFO FROM ACN 368627: AT THE TIME OF THE WARNING WE WERE 1500 FT AGL AND DOING EVERYTHING POSSIBLE TO INCREASE OUR CLB PERFORMANCE!