"downward gradient" is correct and usable in written English.
You can use the phrase to refer to a situation in which something is decreasing or diminishing. For example, "The company's profits showed a downward gradient in the second quarter of the year."
With some exceptions e.g., large apartment complexes in downtown Chicago people do not reside in the downtown areas, and there is a steady downward gradient in population density per unit area (and more open land and single-family residences) as one moves from the inner city toward the open country.
With just 1,700 feet of runway length, this airport has a downward gradient of 18.5%.
At the bottom of the cliff, the trail takes on a gentler downward gradient through an open canyon.
The limited pond data available from Char Para indicate a more pronounced difference of 2 m between the pond and groundwater (downward gradient of 0.2) in June 2009 and no significant gradient later in August through October.
We first examined the pattern of H3K9me2 in normal cochlear epithelium using immunohistochemistry. H3K9me2 staining showed a punctate distribution in virtually all the hair cells, with the strongest signal observed at the edge of outer hair cells and a downward gradient leading to dramatically decreased staining in the inner hair cells.
During the year, reversals in vertical head gradient yield reversals in arsenic temporal trend, and downward gradients in the dry season correlate with increases in arsenic.
In contrast, an indefinite trend (rs187269 and rs1816071) or downward trend (rs6556547 and rs1816072) was observed over these five populations for the schizophrenic samples; the reasons for the two downward gradients yet remain to be understood, but it is not ruled out that assortative mating, which has been observed in schizophrenia [38], might be a contributing factor.
In effect, an overall management strategy of generally decreased pumping in areas of downward gradients and generally increased pumping in areas of upward gradients could help optimize wellbore flow to reduce arsenic concentrations while having little effect on total withdrawals.
Also, the increased contribution of shallow water reaching shallower supply wells as a result of enhanced downward gradients during the summer pumping season might substantially exceed the deep storage of any wellbore flow that occurs during winter idle periods.
Thus, the removal of deep groundwater may only cause the fraction of young groundwater to increase to about 20%; although it should be noted that long-term pumping could cause the fraction of young groundwater to increase as persistent and increasing downward gradients promote larger volumes of young groundwater to migrate to deeper depths.
It indicates that at the curve ahead, the road narrows, and after the second turn, the road begins to turn into a steep (15% gradient) downward slope.
