Smithville Lake Water Quality

Clay County samples water quality at all designated swimming beaches at Smithville Lake on a biweekly basis during the recreational season. The Missouri Department of Natural Resources has designated Smithville Lake as a body of water (lake) with recreational use category Whole Body Contact, category A (WBC-A).

Water samples are analyzed for E coli, a common indicator species for bacteria. It is normal for E coli and other bacteria to be found at naturally-occurring levels in ponds, streams, rivers, lakes, and reservoirs. Elevated bacteria levels are frequently associated with heavy rains; however, there are a number of other sources that may contribute to elevated bacteria levels, which may pose a health risk.

Sample Collection Date	Little Platte Beach Left	Little Platte Beach Right	Little Platte Beach GeoMean	Camp Branch Beach  Left	Camp Branch Beach  Right	Cramp Branch Beach  GeoMean
May 04, 2023	4	4	4	1	8	3
May 18, 2023	845	400	581	235	200	217
May 24, 2023	370	160	243	140	170	154
May 31, 2023	1038	2000	1441	1920	1060	1427
June 15, 2023	829	253	458	675	1585	1034
June 29, 2023	3	1	2	5	36	13
July 12, 2023	25	10	16	30	57	41
July 26, 2023	62	96	77	13	113	38
August 9, 2023	31	24	27	44	96	65
August 23, 2023	96	66	80	260	50	114

Water sample results can help visitors decide whether a particular beach is suitable for swimming, based on the bacteria levels. For waters designated as WBC-A, the state water quality standard is 126 E Coli colonies per 100mL of water during the recreational season (May 1 to September 1). Because of temporary fluctuations, MDNR uses a single event threshold of 190 colonies/100mL of water for E Coli concentrations. Clay County will post signs notifying visitors that swimming is not recommended if the geometric mean of the weekly water quality sample results exceeds the equivalent of 190 E coli colonies per 100 milliliters of water (190 mpn/100 ml).