Groundwater vs. surface water, state by state

Share of each state's active public water systems whose primary source is groundwater (including purchased groundwater) vs. surface water. Nationally, 90.4% of systems draw on groundwater and 9.6% on surface water.

Dataset updated October 2026 . Source: EPA SDWIS/ECHO, refreshed quarterly.

States ranked by groundwater share of active public water systems
#	State	Groundwater share	Groundwater systems	Surface-water systems	All systems
1	Wisconsin	99.4%	10,993	63	11,056
2	Mississippi	98.8%	1,119	14	1,133
3	Minnesota	98.5%	6,367	98	6,465
4	Delaware	98%	484	10	494
5	Florida	97.9%	5,088	109	5,197
6	Nebraska	97.4%	1,194	32	1,226
7	Maryland	97.3%	2,912	79	2,992
8	New Hampshire	97.3%	2,384	66	2,450
9	Indiana	97.2%	3,857	112	3,969
10	Michigan	96.9%	10,269	330	10,599
11	Maine	96.3%	1,793	69	1,862
12	Connecticut	96.2%	2,273	90	2,363
13	Idaho	95.9%	1,880	81	1,961
14	New Jersey	95.5%	3,339	157	3,496
15	Arizona	95.3%	1,686	83	1,769
16	Washington	94.2%	4,432	270	4,705
17	Rhode Island	93.8%	436	29	465
18	Pennsylvania	93.2%	6,727	490	7,217
19	Vermont	93%	1,262	95	1,357
20	New Mexico	92.8%	1,081	84	1,165
21	Hawaii	92.6%	126	10	136
22	Ohio	92.4%	3,561	293	3,854
23	Louisiana	92.3%	1,035	86	1,121
24	Iowa	92.2%	1,685	143	1,828
25	Missouri	91.9%	2,704	239	2,943
26	New York	91.3%	7,459	695	8,167
27	North Carolina	90.9%	4,623	463	5,087
28	Georgia	89.9%	2,134	241	2,375
29	Virginia	88.8%	2,148	272	2,420
30	Montana	88.6%	2,106	272	2,378
31	Nevada	88.2%	567	76	643
32	Oregon	87.5%	2,220	316	2,536
33	Massachusetts	87.5%	1,432	202	1,636
34	Utah	86.7%	982	151	1,133
35	California	85.1%	6,361	1,115	7,479
36	Alaska	83.6%	1,105	217	1,322
37	Wyoming	83.4%	646	129	775
38	Illinois	81.7%	3,164	708	3,872
39	Tennessee	80.3%	1,111	272	1,383
40	Texas	78.5%	5,555	1,520	7,078
41	South Dakota	76.3%	533	166	699
42	North Dakota	74.4%	300	103	403
43	Colorado	74.4%	1,642	565	2,207
44	South Carolina	69.8%	971	421	1,392
45	Kansas	66.1%	688	353	1,041
46	West Virginia	64.7%	512	279	791
47	Arkansas	63.4%	541	312	853
48	Oklahoma	62.2%	780	474	1,254
49	Alabama	60.1%	346	230	576
50	District of Columbia	50%	6	6	12
51	Kentucky	30.9%	135	302	437