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@@ -130,8 +130,13 @@ The following procedures are implemented to ascertain data quality in the databa
 
     CONSTRAINT check_catchment_area_range CHECK ( catchment_area_km2 > 0 AND catchment_area_km2 < 7000000 )
     </details>
-  - further examples
+- Values are checked based on values in other columns:
+  - If a measurement is marked as below an analytical limit, the value of the limit must be given in the corresponding column.
+    <details><summary>Example</summary>
+    If a measurement is marked as below the analytical limit of detection (LOD), the LOD must be given in the corresponding column.
 
+    CONSTRAINT  check_lod_available CHECK ((lod > 0 AND value_below_lod IS TRUE) OR (value_below_lod IS NOT TRUE))
+    </details>
 - Quality assessment workflow: As described below.
 
 ### Quality assessment workflow