Maryland will implement a staged process for defining drought conditions. Drought indicators will be monitored on an ongoing, year-round basis, and drought status will be determined on a variable timeframe according to drought stage (See Tables 1 and 2 below). The frequency of evaluation will increase if the drought intensifies as indicated below:
- Stage 1 Monthly
- Stage 2 Bi-weekly
- Stage 3 Weekly
- Stage 4 Weekly or as needed
Stage 1 – Normal (Green)
No more than one indicator outside of the normal range.
- Precipitation exceeds the percent of normal precipitation for the time period in Table 2
- Streamflows are above the 25th percentile
- Ground water levels are above the 25th percentile
- Reservoirs exceed 120 days of storage
Stage 2 – Watch (Yellow)
At least 2 indicators meet the following conditions:
- Precipitation levels are at or below the percent of normal precipitation for the time period in Table 2
- Streamflows fall between the 10th and 25th percentile
- Ground water levels fall between the 10th and 25th percentile
- Reservoirs contain between 90 and 120 days of storage
Stage 3 – Warning (Orange)
At least 2 indicators meet the following conditions:
- Precipitation levels are at or below the percent of normal precipitation for the time period in Table 2
- Streamflows fall between the 5th and 10th percentile
- Ground water levels fall between the 5th and 10th percentile
- Reservoirs contain between 60 and 90 days of storage
Stage 4 – Emergency (Red)
At least 2 indicators meet the following conditions:
- Precipitation levels are at or below the percent of normal precipitation for the time period in Table 2
- Streamflows are at or below the 5th percentile
- Ground water levels are at or below the 5th percentile
- Reservoirs contain 60 days or less of storage
| |
Precipitation As Percent of Normal for Evaluation
Period 1
|
Streamflow As Percentile of Normal2
|
Ground Water
Levels As
Percentile
of Normal2
|
Reservoir Storage in days
|
|
Stage 1
Normal
|
See Table 2
|
>25
|
>25
|
>120
|
|
Stage 2
Watch
|
25
|
25
|
120
|
|
Stage 3 Warning
|
10
|
10
|
90
|
|
Stage 4
Emergency
|
5
|
5
|
60
|
|
1 These values vary depending of length of review period. For more detail see Precipitation discussion and Table 2.
2 At the 25th percentile, it means that historical streamflows or ground water levels are lower than this value only 25% of the time for the evaluation period. 10th and 5th percentiles represent increasingly lower streamflows or ground water levels and more severe drought events.
|
TABLE 2. Precipitation Triggers
|
Number of Months
Analyzed
|
Normal
(% of
Normal
Precipitation)
|
Watch
(% of
Normal
Precipitation)
|
Warning
(% of
Normal
Precipitation)
|
Emergency
(% of
Normal
Precipitation)
|
|
3
|
>75.0
|
75.0
|
65.0
|
55.0
|
|
4
|
>80.0
|
80.0
|
70.0
|
60.0
|
|
5
|
>80.0
|
80.0
|
70.0
|
60.0
|
|
6
|
>80.0
|
80.0
|
70.0
|
60.0
|
|
7
|
>81.5
|
81.5
|
71.5
|
61.5
|
|
8
|
>82.5
|
82.5
|
72.5
|
62.5
|
|
9
|
>83.5
|
83.5
|
73.5
|
63.5
|
|
10
|
>85.0
|
85.0
|
75.0
|
65.0
|
|
11
|
>85.0
|
85.0
|
75.0
|
65.0
|
|
12
|
>85.0
|
85.0
|
75.0
|
65.0
|
Related Topics
What Can You Do?
For More Information
For more information, contact the Water Supply Program at 410-537-3702 or water.supply@maryland.gov
