What are the differences between low impact development and green infrastructure in hydrology terms?

First of all, it is better to present the definitions of both concepts, then after, we will try to reveal the differences between two techniques:

LID: Low Impact Development (LID) is an alternative to conventional urban stormwater management practices, which aims at mitigating the impacts of urbanization on water quantity and quality. It refers to systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat (Hoghooghi et al., 2018).

LID is defined as "an approach to land development (or re-development) that works with nature to manage stormwater as close to its source as possible. LID employs principles such as preserving and recreating natural landscape features, minimizing effective imperviousness to create functional and appealing site drainage that treat stormwater as a resource rather than a waste product. (EPA)"

GI: "Green infrastructure" (GI) is a relatively new and flexible term, promoted by USEPA. EPA intends the term "green infrastructure" to generally refer to systems and practices that use or mimic natural processes to infiltrate, evapotranspiration (the return of water to the atmosphere either through evaporation or by plants), or reuse stormwater or runoff on the site where it is generated (Figure 2). Green infrastructure can be used at a wide range of landscape scales in place of, or in addition to, more traditional stormwater control elements to support the principles of LID.

LID vs. GI

1- It can be observed that GI refers principally to the control practices used to implement LID, and thus with respect to the control measures the two terms overlap. The principal difference between the two concepts is that LID has a very specific target of maintaining pre-development hydrology. This implies that a thorough hydrologic analysis is required to determine whether a project achieves LID status. As a consequence of this requirement, a considerable amount of technical guidance has been developed to guide the application of LID technology. GI technology does not currently have the same focus. The focus of GI is on the design of the individual GI practices rather than a project or site scale approach. Thus it is possible to implement GI practices without achieving the goal of LID with respect to maintaining pre-development site hydrology\.The two concepts can be combined for a comprehensive and successful application (Clar et al., 1998).

2- LID can be seen as a subset of practices/approaches within the green infrastructure. The difference between the two terms is really one of scale. LID refers to designing and implementing practices that can be employed at the site-level to control stormwater and strive to replicate the pre-development hydrology of the site. Green infrastructure generally refers to a broader, big-picture view of a community or watershed and focuses on a coordinated effort to employ these practices along with practices like land conservation.

Considered collectively, GI is an integrated system of natural elements and LID practices that provide broad environmental benefits. For many, GI is becoming an umbrella term under which other terms, such as LID, fit.

As we see in the bellow table, GI and LID have the same practices.

EPA 2012 - GI and LID