(CNN)Officials tasked with carrying out the nation's border security mission are facing a trifecta of migration challenges, along the US-Mexico border, according to officials, as President Donald Trump announces he will declare a national emergency.
What the Trump administration says is happening at the border
A migrant caravan has made its way to the Texas border, more family members are being apprehended than ever before and numerous large groups of Central American migrants are crossing illegally into the US.
Congressional Democrats have pushed back on the White House plans, arguing that the President is fearmongering and that the situation on the border in no way qualifies as a national emergency.
"No sensible person believes there is an emergency at the southern border. Illegal immigration is at record lows, and families with children who lawfully seek asylum are not foreign invaders," said House Judiciary Committee Chairman Jerry Nadler (D-New York), in a statement Thursday. Nadler said he will support a resolution to terminate the President's emergency declaration, should he issue one.
As debate continues over the effectiveness and practicality of a wall, there are a number of potential flash points along the southern border.
Here's what federal officials say they are facing.
Federal and local law enforcement descended on the normally quiet town of Eagle Pass, Texas, as a nearly 2,000 person migrant caravan arrived on the Mexican side of the border a week ago.
Separately, over the last several months, the US Border Patrol has been encountering an unprecedented number of large groups -- defined as over 100 people -- illegally crossing the southern border, often in remote areas.
"They are in fact two varying phenomena that in some ways have certainly similar challenges for us, but now very clearly are intersecting at times," said Customs and Border Protection Deputy Commissioner Robert Perez.
At the same time there's been a notable shift in the demographics of undocumented migrants at the southern border. While the number of apprehensions of illegal crossings is nowhere near its peak of more than 1.6 million nearly 20 years ago, children and families now make the majority of Border Patrol arrests.
For the first four months of the fiscal year, nearly 60% of all Border Patrol apprehensions were families and unaccompanied children, according to Perez. For all of fiscal year 2018, families and unaccompanied children were around 40% of the total number of apprehensions.
The change has strained law enforcement resources and created new challenges for processing migrants, according to CBP officials.
For instance, Border Patrol aims to move migrants out of custody within 72 hours, but a CBP official last week said that "it's difficult and we often go over the 72 hours."
"It's very difficult to meet that timeline," added the official.
The combination of families, large groups and caravans has stressed CBP resources "to the very edge," said Perez.
"The cost, the time, everything, it puts stresses in the entirety of the system," he added.
On Monday, US Border Patrol apprehended the highest number of family members on a single day. More than 2,000 family members were arrested after crossing the border illegally. The previous record was on December 3 when 1,581 family members were apprehended, according to a CBP official.
In December, US Border Patrol arrested 27,518 family members, a monthly record, which was up nearly 240% from last December, which had 8,120 arrests.
Historically, Border Patrol arrested primarily single adults from Mexico. Those regional demographics have also shifted and now US authorities are encountering a majority of families and children from Central American countries.
"November was the first month in recorded history where more people arrived from another country than Mexico," said CBP Commissioner Kevin McAleenan during congressional testimony in December. Guatemala exceeded Mexico by 3,000 people, he said.
In January, both total apprehensions of migrants -- including families -- at the southern border ticked down, in line with seasonal drops in illegal migration, according to monthly CBP data released Friday.
While historically there are decreases in illegal border crossings from December to January, "this decrease is one of the lowest that we've had on record," said a CBP official last week.
The number of unaccompanied minors crossing the southern border illegally went up slightly from December to January. And while the number of family members illegally crossing went down, it still remains relatively high.
The number of large groups -- more than 100 people -- encountered by Border Patrol skyrocketed to at least 60 groups so far this fiscal year, up from 13 groups last year and only two groups the year before that, according to the same CBP official.
"It's not just the size of group, but the makeup and where the groups are entering," said the official. Groups are arriving in "very remote, very rugged, harsh environments," added the official.
For example, in the last week, a group of over 300 people were apprehended in Ajo, Arizona, and another group of just under 300 people was apprehended in Lordsburg, New Mexico. Another two groups of more than 300 migrants crossed the border in the El Paso region earlier this week, according to another CBP official.
These groups have been made up of primarily Guatemalans, with some other Central Americans, said Perez.
In addition, the overall number of Border Patrol medical referrals for migrants to outside services is on track to reach 28,000 this fiscal year, based on current numbers. Last year there were 12,000 "secondary medical" referrals," said the CBP official.
"Unlike ever before we continue to make upwards, on average, of about 50 trips a day to the hospital, 50 a day," said Perez about the number of trips at Border Patrol agents make to care for arrested migrants.
"A huge amount of these folks are very vulnerable populations. They're families, they're children, they're mothers, they're fathers. In addition to that they're are presenting already ill many times or at least with some sort of illness that requires medical intervention," said Perez.
Perez said this presents a challenge to CBP, "unlike anything I've ever seen."
Around 1,800 migrants were being housed in the Mexican border town of Piedras Negras across the Rio Grande from Eagle Pass, Texas, while they await the opportunity to try to enter the US.
Perez said the US government, "as always," is encouraging people to present lawfully at the port of entry.
Typically the port of entry allows about 15 undocumented migrants people to be processed at Eagle Pass, but in the wake of the caravan's arrival CBP officers have been added to increase processing to about 20 people each day, according to Perez.
"The fact is that Eagle Pass is not a very big place," Perez said. "There's limited capacity there."
Immigration advocates argue that rather than limiting the number of asylum seekers allowed into the US, the government should address the humanitarian crisis at the border by increasing processing capabilities at the ports.
"This country is more than capable of protecting the health and safety of asylum seekers and migrants who reach our border," wrote Human Rights First's Eleanor Acer after Jakelin Caal Maquin, a seven-year-old girl, died in Border Patrol custody.
Jakelin and 8-year-old Felipe Alonzo-Gomez both died in December after being apprehended by Border Patrol. The children's deaths prompted CBP to take a series of steps to enhance medical screening for migrants arriving at the southern border.
"Instead of subjecting fleeing families to cruel and punitive treatment, the administration should address the humanitarian crisis at the border by ending the illegal practice of turning away asylum seekers at ports of entry, increasing capacity for processing asylum claims at ports, and moving away from policies meant to punish those seeking safety," added Acer.
Advocates also argue that the so-called "metering" of migrants at the border has put vulnerable populations at risk and created backlogs of asylum seekers.
CBP officials argue that they are doing the most they can with the resources they have.
The resources available for the agency's humanitarian mission are limited by the physical infrastructure at the port, as well as other mission priorities such as facilitating legal trade and travel, as well as other enforcement actions, according to CBP officials.
Last week, the migrants began arriving along the border across from Eagle Pass on more than 50 buses.
Most of the migrants in the caravan are from Honduras, with some from Guatemala and El Salvador as well, Guatemalan Consul Tekandi Paniagua in Del Rio, Texas said last Monday.
The caravans, a different phenomena than the large groups, have been primarily made up of Honduran migrants, along with other Central Americans, according to Perez.
To deal with the most recent caravan, Customs and Border Protection deployed 150 personnel and is working with Department of Defense partners, as well as local law enforcement to line the border.
The Pentagon announced it was moving approximately 250 active duty US military personnel to the region and Republican Texas Governor Greg Abbott, sent 500 officers from the department of public safety to Eagle Pass, according to Mayor Ramsey English Cantu.
Last week, CBP said in a press release it was taking security measures to ensure that the port of entry was "not overrun," including the deployment of "Connex containers, K-Rails and several spools of Concertina Wire (c-wire)," CBP said in a release.
This group of migrants arrived at the Texas border only a couple months after a caravan of thousands of people in Tijuana grabbed national headlines.
Just after Thanksgiving, while the thousands of migrants waited south of San Diego to enter the US, a group of migrants rushed the border, forcing the closure of one of the busiest international ports, and leading Border Patrol agents to fire tear gas at the group.
The incident sparked outrage after images of the scene showed a cloud of tear gas that sent people running and screaming, including families with young children.
At the time, McAlleenan said the use of force was necessary to disperse the crowd after an "assault on agents and officers."
CBP said that it's currently monitoring a "particularly large group" of migrants that is gathered in the southern tier of Mexico, as well as tracking a smaller group that may be beginning to organize in Honduras.
"We've been monitoring and keeping a close eye on the development of these for some time now and we will continue to do so to make sure that we are prepared," said Perez.
The agreement reached by congressional negotiators appears to cover about half of the miles requested by CBP in the Rio Grande Valley.
A senior CBP official on Tuesday confirmed that, if funded, "most of [the] new mileage" CBP has prioritized would be in the Rio Grande Valley -- more than 100 miles. There would also be additional miles in San Diego, Yuma and Laredo, but the bulk of new linear mileage on primarily border l