Drivers of groundwater utilization in water-limited rice production systems in Nepal
Urfels, Anton ; McDonald, Andrew J. ; Krupnik, Timothy J. ; Oel, Pieter R. van - \ 2020
Water International 45 (2020)1. - ISSN 0250-8060 - p. 39 - 59.
decision processes - Eastern Gangetic Plains - Groundwater irrigation - Nepal - resilience - smallholders
Most rice farmers in Nepal’s Terai region do not fully utilize irrigation during breaks in monsoon rainfall. This leads to yield losses despite abundant groundwater resources and ongoing expansion of diesel pumps and tubewell infrastructure. We investigate this puzzle by characterizing delay factors governing tubewell irrigation across wealth and precipitation gradients. After the decision to irrigate, different factors delay irrigation by roughly one week. While more sustainable and inexpensive energy for pumping may eventually catalyze transformative change, we identify near-term interventions that may increase rice farmers’ resilience to water stress in smallholder-dominated farming communities based on prevailing types of irrigation infrastructure.
Blood Platelet Production: Optimization by Dynamic Programming and Simulation
Haijema, R. ; Wal, J. van der; Dijk, N.M. van - \ 2007
Computers and Operations Research 34 (2007)3. - ISSN 0305-0548 - p. 760 - 779.
optimal ordering policies - perishable-inventory - decision processes - management - model - approximations - bank
Blood platelets are precious, as voluntarily supplied by donors, and highly perishable, with limited lifetimes of 5¿7 days. Demand is highly variable and uncertain. A practical production and inventory rule is strived for that minimizes shortages and spill. The demand and production are periodic, as varying over the seven days of the week. Demand for `young¿ platelets (oncology and hematology) and demand for platelets of `any¿ age up to the maximal shelf life (traumatology and general surgery) are distinguished. A combined Markov dynamic programming (MDP) and simulation approach is presented and applied to a real life case of a Dutch blood bank. By down-sizing the dimension and applying this combined approach it is shown that order-up-to type replenishment rules that perform quite well can be found. Particularly, a double-level order-up-to rule, so-called 2D rule, is derived, with one level corresponding to `young¿ platelets and one to the total inventory. This rule is easy to implement and is shown to be `nearly optimal¿. This approach and the double order-up-to rule seem to be new. The results are most suitable for sensitivity analyses such as with respect to shortages and production costs for blood platelet inventory management.