diff --git a/wut-water-range b/wut-water-range
index dc22b1a..cbb565d 100755
--- a/wut-water-range
+++ b/wut-water-range
@@ -9,9 +9,22 @@
 #
 # The last observation to start in 2019 was 1470525
 # The last observation to start in 2019-11 was 1292461
+#
+# APPROXIMATE:
+# Observations 2015: 1-86
+# Observations 2016: 87-613. Many in 15,000 range too
+# Observations 2017: 614-55551
+# Observations 2018: 55551-388962
+# Observations 2019: 388963-1470939
+# Observations 2020: 1470940-3394851
+# Observations 2021: 3394852-5231193
+# Observations 2022-01 2022-04: 5231194-5712616
+#
 # NOTE! Observations are not in numerical order by chronology.
 # It looks like it is ordered by scheduling, so an older observation can have
-# a higher observation ID.
+# a higher observation ID. So the above list is rough, not exact.
+# Also, there are exceptions, such as observations with IDs far higher than
+# others that year.
 #
 # So to get mostly all of the observations in December, 2019, run:
 # wut-water-range 1292461 1470525