To do that, you must write them so that they are easy to understand, and that they invite the reader to read all the way to the end. When you finish your first draft, put it to the test. You are working for a project that has several donors, and is channelled through an agency that needs to be informed about some specific things going on in the field. Your reports are the main pathways or channels of information to the people who decide to fund this and other such projects. To be concise means that they should be both brief and complete.
Short reports are more likely to be read than long reports.
But reports that miss important information are disappointing. A report is easier to read when it is written in simple, straight forward language, with correct grammar and words easily recognized. Do not try to impress anyone with flowery language, esoteric vocabulary, or long and convoluted sentences. Use short, simple sentences. Use short paragraphs.