How do salva and nya overcome adversity? What theme might be the author be developing through these characters?

​In A Long Walk to Water both Nya and Salva show persistence in challenging environments. Nya has to walk eight hours every day to the pond and back to gather water. She must continue no matter what. “There it was, a big thorn that had broken off right in the middle of her heel. Nya pushed at the skin around the thorn… She pressed her lips together against the pain.” This quote shows that Nya must persist through challenging environments because the thorn got stuck in her heel and she must push through the pain to get to the pond. If she does not make it to the pond then her family will not have the water that they need. Salva had to leave his village because the war struck. He now must walk all day, every day to find safety. The environment challenges him by making him dehydrated and both mentally and physically hurt. “Uncle cautioned him to make the water in his gourd last as long as possible. It was the hardest thing Salva had ever done, taking only tiny sips when his body cried out for huge gulps of thirst-quenching, life-giving water. The worst moment of the day happened near the end. Salva stubbed his bare toe on a rock, and his whole toenail came off. The pain was terrible.” This shows Salva’s persistence because despite the pain he is able to push through and continue to walk through the desert.