Table:
text: List of townships in North Dakota
B
B
Township County Pop_2010 Land_sqmi_ Water_sqmi Latitude Longitude GEO_ID ANSI_code
Blanchard Traill 87 36.012 0.000 47.367463 -97.282684 3809707660 01036685
Bloom Stutsman 554 33.776 0.573 46.942845 -98.618900 3809307740 01036469
Bloomenfield Stutsman 34 34.280 1.742 46.747452 -99.279759 3809307780 01036463
Bloomfield Traill 130 36.059 0.000 47.367479 -97.155083 3809707820 01036682
Blooming Grand Forks 295 34.525 0.329 47.972550 -97.297617 3803507860 01036605
Blooming Prairie Divide 50 42.168 1.102 48.945295 -103.395531 3802307900 01036928
Blooming Valley Divide 47 35.564 0.528 48.851356 -103.135611 3802307940 01759387
Blue Butte McKenzie 79 34.495 1.183 47.886549 -102.953006 3805308020 01036961
Blue Hill McLean 16 35.876 0.079 47.790088 -101.669787 3805508060 01759528
Blue Ridge Williams 35 33.932 2.121 48.585864 -103.590163 3810508100 01037004
Bluebird LaMoure 35 35.572 0.060 46.499580 -98.848322 3804507980 01036907

text: List of townships in North Dakota
B
B
Township County Pop_2010 Land_sqmi_ Water_sqmi Latitude Longitude GEO_ID ANSI_code
Brander Bottineau 54 35.726 0.265 48.755867 -101.026977 3800909060 01759268
Brandon Renville 72 34.743 0.130 48.747978 -101.570983 3807509100 01759599
Bremen Wells 47 35.825 0.238 47.709329 -99.350957 3810309260 01759696
Brenna Grand Forks 725 35.983 0.027 47.888770 -97.171507 3803509300 01036602
Brightwood Richland 203 32.696 1.977 46.069255 -96.936548 3807709340 01036821
Brillian Ward 57 36.200 0.012 47.980022 -101.034374 3810109380 01759674
Brimer Barnes 59 35.524 0.452 47.015788 -98.393490 3800309420 01036433
Brittian Hettinger 17 35.700 0.077 46.303491 -102.218605 3804109580 01759448
Broadlawn Steele 41 35.250 0.062 47.279320 -97.508269 3809109620 01036657
Broadview Griggs 38 33.916 1.469 47.281208 -98.012284 3803909660 01036629
Broe Benson 35 35.497 0.546 48.146770 -99.641921 3800509740 01759238
Brookbank Mountrail 34 35.908 0.012 48.158814 -102.500392 3806109780 01037114

Question: What is the average water sqmi among the list of communities in North Dakota, B with a population (2010) greater than 47 in the community of Brenna with longitude less than -97.171507?