WASHINGTON — KURDS may be trickling back to their homes in northern Iraq, but the world's refugee crisis goes on. Never before have so many people who have fled their homes needed so much help in so many inaccessible parts of the globe.The latest estimate by the private US Committee for Refugees now puts the world's refugee population at more than 18 million. And many of the worst situations - Afghanistan, Ethiopia, Somalia - show no signs of being resolved, according to the head of the United Nations' refugee programs. "We won't have fewer refugees in the foreseeable future," says Sadako Ogata, a former Japanese delegate to the General Assembly who has been UN High Commissioner for Refugees (UNHCR) since February. At the same time, the nature of refugee flows is changing. Once made up mostly of civilians driven across national boundaries by wars, they are increasingly mixed with migrants trying to escape poverty, tribal groups persecuted in ethnic upheaval, and others who have simply been uprooted from one part of their country and shuffled to another. This mass movement of people around the world today, which includes refugees, totals upwards of 30 million, according to a UNHCR estimate. Hardly any corner of the world is unaffected. The failure of communist countries, followed by economic disintegration, threatens to swell the outflow further. Mrs. Ogata says she doubts a Soviet collapse will send streams of people westward, but adds that the office of the UNHCR is planning education programs in Eastern Europe, hoping to convince people to stay home by giving them a more realistic view of what might await them over the border. "The Europeans are very much afraid of this massive increase of asylum seekers," she says. Though in office only four months, the new UNHCR head has already undergone the baptism by fire of the Iraqi refugee situation. With most Kurds now well on their way home the situation is being resolved faster than the UN had expected. Ogata worries, however, about how safe northern Iraq will be once coalition military forces pull out. She has appealed for a relatively slow military withdrawal, and praises the possibility of an allied rapid deployment force in Turkey as a "positive development." In the past, the UNHCR has largely jumped in to feed and house refugees only after they have crossed international boundaries. By operating inside the borders of the nation which forced the Kurdish refugees to flee in the first place, "we've crossed a threshold" in Iraq, says Ogata. Building some sort of right of humanitarian access to help internally displaced people will be one of the most important refugee issues of coming years, the UNHCR points out. In recent months this has been been a problem not only in Iraq but in Africa as well. In Mozambique, the government and RENAMO rebels agreed to a so-called "corridor of tranquillity" to allow safe passage of humanitarian aid. Tinkering with the office of the UNHCR to improve its ability to respond to emergencies is also on Ogata's agenda. "It's a very cumbersome, difficult structure," she sighs. The UNHCR office gets most of its money by going hat in hand on appeals to the world community after a refugee situation develops. It has only a relatively small $20 million emergency fund for seed money. For instance, the UN estimates its Kurdish refugee operations will cost $267 million. So far, only about $170 million has been collected. There's no chance of the UNHCR office being funded by regular assessed contributions. But Ogata says of the emergency fund "either this has to be increased or maybe the UN system will have to come up with a common emergency fund." Typically the US pays for about 25 percent of UNHCR's activities. Through June, the United States contribution has been $120 million toward UNCHR's overall $800 million 1991 budget. "This is the same amount the US gave all last year, and it is only June," says Ogata. "Hopefully through the end of the year there will be considerably more."