Drought in Delaware

Note:  The next drought report will be on November 26th, 2025

Highlights:

• Below normal precipitation and higher evapotranspiration rates have continued since mid-October, further increasing the water balance deficits across the state. 
• Soil moisture conditions have continued to decline in October-November, with most of the state having below normal conditions for this time of year
• Streamflow conditions have continued to decline for most areas of the state due to the continued water balance deficits in August and September.  This has significantly increased the chloride levels on the Christina and Delaware.
• Groundwater conditions are mixed throughout the state, though most monitoring wells are currently in the normal range for this time of year
• A La Nina event is expected to develop by early winter, which tends to lead to drier and warmer conditions for Delaware during the winter months

Statewide Drought Discussion

Dry conditions have persisted throughout Delaware this fall, with some portions of the state experiencing moderate drought conditions. 

Precipitation

Most of Delaware has continued to see lower than normal precipitation, with the only exceptions being portions of northern New Castle County and eastern Sussex County, which have seen 2.5 to 3.5 inches over the last 30 days (Figure 1).

The dry fall weather has led to statewide precipitation deficits on the order of 2 to 4 inches at 60 days and 2 to 6 inches at 90 days.  While these precipitation deficits have contributed to the return of moderate drought conditions to portions of the state, these are substantially less significant than the precipitation deficits experienced in 2024, which led to one of the rapidly intensifying droughts in state history.  

Temperature/Evapotranspiration

Temperatures over the last 30 to 60 days have been normal to slightly below normal, which tends to keep evapotranspiration lower.  However, because of the drier than normal weather conditions, evapotranspiration rates have been above normal, since dry days mean less humidity and higher solar radiation conditions (Figure 2).

With higher evapotranspiration rates and lower than normal precipitation, water balance deficits have developed throughout the fall, leading to dry conditions and some drought across Delaware.

Soil Moisture

Soil moisture levels in the top meter of soil remain below the 10th percentile across much of Delaware (Figure 3).  

About the only part of the state with near normal soil moisture conditions is the Piedmont area, which is generally all of New Castle County north of I-95.  This area tends to have higher water holding capacity soils that don’t dry out as quickly after a rain event, especially in the cool season.  Meanwhile, southern Kent County and most of Sussex County, where we have sandier soils that dry out very quickly, are well below normal relative to the last 15+ years.

Streamflow

During October and into November, streamflows across Delaware have remained at the low end of  normal (25th percentile), which indicates much drier-than-normal conditions. During the first couple of weeks in November, streamflows have stayed low despite cooler temperatures. In northern New Castle County, low flows limit the natural dilution of chlorides that encroach from the Delaware River, affecting water quality and increasing challenges for surface-water suppliers. Unless northern Delaware experiences more widespread and consistent rainfall later in the month, the below-normal flows may persist into the winter, which will warrant continued monitoring of regional hydrologic conditions. Further south in Kent and Sussex Counties, streamflows are also well below normal, continuing a trend that has persisted since October. (Table 1)

Chlorides

Recent precipitation has diluted chloride levels in the Christina River near Newport to 442 ppm after reaching a high of 1165 ppm at the end of October. This decrease is largely due to increased river flows in recent days, which have allowed fresh water to dilute the tidal saltwater, pushing the chlorides further downstream toward the mouth of the Christiana River. Without rainfall to continue dilution, chloride concentrations may again rise to concentrations seen at the end of October.  Elevated chloride levels can speed up the corrosion of pipes, bridges, and other infrastructure, leading to higher maintenance costs and a greater risk of damage. They also pose a threat to aquatic ecosystems, as fish, insects, and plants in freshwater streams are especially sensitive to changes in salinity.

On the Delaware River, the typical November median salt front position is around River Mile 70 (near the  mouth of the Christina River), meaning the current location (River Mile 88.3) is noticeably farther upstream than average for this time of year. Continued monitoring through late fall and early winter will help assess whether upcoming rainfall and river discharge push the salt front back downstream toward its usual seasonal position.

Groundwater

Groundwater levels across Delaware showed mixed conditions in October, reflecting the effects of several dry months. In northern New Castle County, water levels in the unconfined (shallow) aquifer have continued to decline. A monitoring well just south of Newark (Db24-18) measured 15.3 feet below land surface, which is below normal for this time of year (typically 12.8 to 14.9 feet below land surface).

Elsewhere in the state, groundwater conditions vary. A groundwater monitoring well in southern New Castle County (Hb12-05) remains at the low end of normal (Figure 4), while another groundwater monitoring well in southwestern Kent County (Mc51-01a) has been declining steadily since late April and remains below the 5th percentile at 16.85 feet below land surface;

potentially a new record low. In southeastern Sussex County, well Pf24-02 has remained within the normal range since May, with a brief period of above-normal levels in early August.

Low groundwater levels—such as those observed in parts of Kent County—can put stress on local water supplies and increase the potential for shortages if dry weather continues into the winter months. Continued monitoring will help track whether recharge improves with late fall and winter precipitation.

Weather and Climate Outlook

As we transition into the “cool” season (November-March), our climate influences shift, with the El Nino-Southern Oscillation (ENSO) becoming increasingly more relevant.  The ENSO has 3 phases:  El Nino, Neutral, and La Nina.  Each phase represents a different sea surface temperature regime in the tropical Pacific, which affects the way weather systems develop and move across North America.  The expectation right now is that a weak La Nina event will develop in the next month or so.  These events tend to lead to warmer and drier winters in the Mid-Atlantic region of the United States.  Thus, NOAA’s Climate Prediction Center’s 3-month temperature and precipitation outlook depict Delaware as likely to experience above normal temperatures and slightly below normal precipitation (Figures 5 and 6).  

Winter is when our surface and groundwater systems recharge the most from precipitation, so this forecast wouldn’t be ideal for that, especially given the recent dryness we’ve been experiencing.  We’ll continue to monitor ENSO to see how intense and how long the La Nina event sticks around.