Upstream decides downstream

Drought has required that ships transiting the Panama Canal float higher. Starting today the largest vessels’ draft cannot be deeper than 43.5 feet (more). Higher in the water means less cargo. Due to this year’s drought Gatun Lake’s water level is almost five feet below its five year average (including a dry 2019) and is forecast to continue dropping. Gatun Lake is itself a travel lane and source of water for the canal’s locks and drinking water for local inhabitants. If water levels continue to fall the number of canal crossings may be reduced. Typically thirty-five or so ships cross the canal each day. Fewer than thirty are now being contemplated.

The Rhine River is also running low (if not, yet, quite as low as last summer). Rain over the last few days has bumped most river gauges just barely above the lowest mean value threshold while sparse rain is forecast for this week. In mid-June, Bloomberg was already reporting, “any barges planning on hauling diesel-type fuel past Kaub (on the Rhine) have been limited to loading just 60% of their maximum carrying capacity.” (More)

Since last week rain has finally returned to the Upper Mississippi watershed. The Missouri River and Lower Mississippi have benefitted from higher-than-average snowmelt and more typical seasonal precipitation. (See preexisting conditions with map below, more). Local farmers hope this is just in time to save spring planting (more). Until this week’s precipitation, the Upper Mississippi seemed threatened by a second year of low flow (here and here). Even with recent (current) rain, downstream levels are still forecast (more) to continue falling.

The literal upstream to downstream dynamics here are important enough. The potential analogies for wider demand and supply networks are worth consideration. Upstream surplus or drought defines downstream capacity. Measures of midstream channel flows are indicative, if less than conclusive, regarding potential supply. Where and when, how widely and for how long, upstream and midstream capacity is constrained will decide what proportion of downstream demand is fulfilled when and where.