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 July 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%	10,990	63	11,053
2	Mississippi	98.8%	1,167	14	1,181
3	Minnesota	98.2%	6,419	115	6,534
4	Delaware	98%	484	10	494
5	Florida	97.9%	5,091	108	5,199
6	New Hampshire	97.3%	2,377	66	2,443
7	Maryland	97.2%	2,989	83	3,074
8	Indiana	97.2%	3,862	113	3,975
9	Michigan	96.9%	10,266	331	10,597
10	Maine	96.3%	1,797	69	1,866
11	Connecticut	96.2%	2,272	90	2,362
12	Idaho	95.9%	1,871	79	1,950
13	New Jersey	95.5%	3,348	157	3,505
14	Arizona	95.3%	1,687	84	1,771
15	Nebraska	95%	1,261	67	1,328
16	Washington	94.2%	4,431	271	4,705
17	Rhode Island	93.8%	436	29	465
18	Pennsylvania	93.3%	6,755	487	7,243
19	Vermont	93%	1,261	95	1,356
20	Hawaii	92.7%	127	10	137
21	Ohio	92.5%	3,727	301	4,028
22	Louisiana	92.3%	1,037	87	1,124
23	Iowa	92.2%	1,681	143	1,824
24	New Mexico	92%	1,094	95	1,189
25	Missouri	92%	2,702	236	2,938
26	New York	91.3%	7,453	698	8,164
27	Georgia	89.8%	2,129	241	2,370
28	North Carolina	89%	4,738	587	5,325
29	Montana	88.6%	2,111	271	2,382
30	Nevada	88.1%	572	77	649
31	Virginia	88%	2,405	327	2,733
32	Massachusetts	87.6%	1,428	202	1,631
33	Oregon	87.5%	2,211	316	2,527
34	Utah	86.8%	989	150	1,139
35	California	84.1%	6,640	1,249	7,892
36	Illinois	83.9%	3,848	737	4,585
37	Alaska	83.4%	1,102	219	1,321
38	Wyoming	83.2%	646	130	776
39	Tennessee	80.6%	1,120	270	1,390
40	Texas	78.5%	5,557	1,517	7,076
41	South Dakota	76.5%	540	166	706
42	North Dakota	74.4%	300	103	403
43	Colorado	74.3%	1,642	567	2,209
44	South Carolina	69.7%	970	422	1,392
45	Kansas	65.9%	681	353	1,034
46	West Virginia	64.7%	518	283	801
47	Arkansas	63.2%	547	318	865
48	Oklahoma	62.4%	796	480	1,276
49	Alabama	60.3%	349	230	579
50	District of Columbia	57.1%	8	6	14
51	Kentucky	30.7%	134	303	437