The latest figures from the Southwest Border show crossings falling, not rising:

USBP	Demographic	OCT	NOV	DEC	JAN	Total
Southwest Border	UAC	3,158	3,981	4,078	3,227	14,444
	Family Units	4,837	7,015	8,120	5,656	25,628
Southwest Border Total Apprehensions		25,487	29,080	28,997	25,980	109,544

Tables are accurate as of 2/1/18, totals change as data is adjudicated.

Southwest Border Migration FY2018

During the month of January, CBP saw a 12 percent decrease in individuals apprehended while trying to enter the country illegally in between established ports of entry, and in those presenting themselves for entry, without proper documentation, along our Southwest border. This is typical of the migration patterns in the month of January. [More]

This chart covers several years, I've circled the dip in this January:

The January figures aren't the big story, just the most recent. The real story is the orange line, for Fiscal Year 2017, "Fiscal Year" starting in October 2016. That shows a massive drop, and that's the Trump Effect.